If the tolerance of the arithmetic sequence {an} is not zero, the first term A1 = 1, and A2 is the equal proportion middle term of A1 and A5, then the sum of the first 10 terms of the sequence {an} is () A. 90B. 100C. 145D. 190

If the tolerance of the arithmetic sequence {an} is not zero, the first term A1 = 1, and A2 is the equal proportion middle term of A1 and A5, then the sum of the first 10 terms of the sequence {an} is () A. 90B. 100C. 145D. 190

According to the meaning of the title, (a1 + D) 2 = A1 (a1 + 4D), that is, A12 + 2a1d + D2 = A12 + 4a1d, ｜ d = 2A1 = 2. ｜ S10 = 10A1 + 10 × 92d = 10 + 90 = 100
It is known that {an} is an arithmetic sequence with non-zero tolerance, A1 = - 10, and A2, A4, A5 are equal proportion sequence. 1) the general formula for finding an
2) If a > 0, find the first n terms and Sn of BN = a ^ [1 / 2 (an + 12)]
1) Let the tolerance be known as D (A4) ^ 2 = A2 * A5, then (a1 + 3D) ^ 2 = (a1 + D) (a1 + 4D) A1 * D + 5D ^ 2 = 05D = - A1 = 10, d = 2, so the general formula an = - 10 + 2 (n-1) = 2n-122) BN = a ^ [(1 / 2) * (an-12)] = a ^ NSN = a + A ^ 2 +. + A ^ n = a * (a ^ n-1) / (A-1) is obtained
Question: Yes, I don't know the second question
Let an be an arithmetic sequence with tolerance D (d unequal and 0), its first n terms and Sn = 110, and A1, A2, A4 are equal proportion sequence. It is proved that A1 = D
A formula for finding the value of tolerance D and sequence an
A2 ^ 2 = a1a4 (a1 + D) ^ 2 = A1 (a1 + 3D) A1 ^ 2 + 2a1d + D ^ 2 = A1 ^ 2 + 3a1da1d = D ^ 2A1 = DA1 = DA2 = D + D = 2da3 = D + 2D = 3D. An = a1 + (n-1) d = D + ND-D = NDSN = D + 2D + 3D +. + nd = D (1 + 2 + 3. + n) = D (n + 1) * n / 2 = 110 = Nd (n + 1) / 2 = 110, the condition may be incomplete, and the value of tolerance D cannot be obtained
In the circuit as shown in the figure, the resistance value of resistance R1 is 20 Ω, and the power supply voltage remains unchanged. When S1 and S2 are disconnected and S3 is closed, the indication of ammeter is 0.45a; when S1 is disconnected and S2 and S3 are closed, the indication of ammeter is 0.75a? (2) What is the resistance of R2? (3) When S2 and S3 are open and S1 is closed, what is the voltage applied to both ends of resistance R1?
(1) When S1 and S2 are open and S3 are closed, R2 is open. I1 = 0.45a, then according to Ohm's law, the power supply voltage U = i1r1 = 0.45a × 20 Ω = 9V; (2) when S1 is open and S2 and S3 are closed, R1 and R2 are connected in parallel, the current of R2 is I2 = i-i1 = 0.75a-0.45a = 0.3A; R2 = ui2 = 9v0.3a = 30 Ω; (3) when
Simple operation of decimals (at least 10)
1,9.56+14.5+5.5=9.56+20=29.562,14.15+2.9+1.85=14.15+1.85+2.9=16+2.9=18.93,4.3+2.05+6.7+0.95=（4.3+6.7）+（2.05+0.95）=11+3=144,3.68+7.65-2.68=3.68-2.68+7.65=1+7.65=8.755,5.17-1.8-3.2=5.17-（1.8+3.2）=...
How to list the vertical form of multiplication
Write out a two digit number, such as 32, and exchange the ten digits of the two digit number with the number on the one digit, then the sum of 23 and 32 is 55, which can be divided by 11
(1) Is there such a conclusion when writing any two digit number? Please have a try;
(2) Can you prove the above conclusion by using a to represent a two digit ten digit number and B to represent a two digit one digit number?
(3) What is the difference between the original number and the obtained number?
It's better to explain why we can and why we can't
(1) 87,78,87 + 78 = 165165 / 11 = 15;
(2) (11a + 10b) = 11a + 10A + 10A + 10B after exchange;
(3) 10A + B - (10b + a) = 10A + b-10b-a = 9A + 9b = 9 (a + b), the difference is always 9 times of the original number
As shown in the figure, the power supply voltage remains unchanged. When switch S1 is closed and S2 and S3 are open, the electric power of resistance R1 is 1.8W and the indication of ammeter is 0.3
Then close the switch S2, and the current is 0.9A
(1) What is the supply voltage?
(2) What are the resistances of R1 and R2?
(3) When the switches S1 and S2 are open and S3 is closed, how much heat is generated on R2 in 3 minutes
The point is the second question and the third question. The first question already knows
(2) because S2 and S3 are open, only S1 is closed, so it is a series circuit (series voltage division, parallel shunt). And because the current through R1 is 0.3A, so the current through R2 is: R circuit - R1 = 0.9a-0.3a = 0.6A, so according to the formula r = u / I, we can know that
Where is the picture????????
The more, the better
（1）98+998+9998+99998
=(100-2)+(1000-2)+(10000-2)+(10000-2)
=100+1000+10000+10000-2-2-2-2
=111100-8
=111092
（2）1127*1123
=(1120+7)*(1120+3)
=1120*1120+1120*3+1120*7+7*3
=1254400+1120*(7+3)+21
=1254400+11200+21
=1265621
The calculation is simple
408－12×24 （46＋28）×60 42×50－1715÷5
32＋105÷5 （108＋47）×52 420×（327－238）
(4121+2389)÷7 671×15-974 469×12+1492
405×(3213-3189) 5000-56×23 125×(97-81)
6942+480÷3 304×32-154 20+80÷4-20＝
100÷（32-30）×0＝ 25×4-12×5＝
70×〔（42-42）÷18〕＝ 75×65+75×35＝
Calculate the following questions in a simple way
1、89+124+11+26+48 2、875-147-23
3．25×125×40×8 4、147×8+8×53
5、125×64 6、0.9＋1.08＋0.92＋0.1
Calculation by simple method
①89+124+11+26+48 ②875-147-23
③147×8+8×53 ④125×64
Calculate the following questions
1．280＋840÷24×5 2．85×(95－1440÷24)
3．58870÷(105＋20×2) 4．80400－(4300＋870÷15)
5．1437×27＋27×563 6．81432÷(13×52＋78)
7．125×(33－1) 8．37.4－(8.6＋7.24－6.6)
Calculation. (1 ∶ 1)
（1）156×107-7729 （2）37.85-（7.85+6.4）
75÷〔138÷（100-54）〕 85×(95－1440÷24)
80400－(4300＋870÷15) 240×78÷（154-115）
1437×27＋27×563 〔75-（12+18）〕÷15
2160÷〔（83-79）×18〕 280＋840÷24×5
325÷13×(266－250) 85×(95－1440÷24)
58870÷(105＋20×2) 1437×27＋27×563
81432÷(13×52＋78) [37.85-（7.85+6.4）] ×30
156×[(17.7-7.2)÷3] （947－599）＋76×64
36×(913－276÷23) [192－（54＋38）]×67
[（7.1-5.6）×0.9-1.15]÷2.5 81432÷(13×52＋78)
5.4÷[2.6×（3.7-2.9）+0.62] （947－599）＋76×64 60－(9.5＋28.9)]÷0.18 2.881÷0.43－0.24×3.5 20×[(2.44－1.8)÷0.4＋0.15] 28-(3.4 1.25×2.4) 0.8×〔15.5-(3.21 5.79)〕 （31.8 3.2×4）÷5 194－64.8÷1.8×0.9 36.72÷4.25×9.9 3.416÷（0.016×35） 0.8×[(10－6.76)÷1.2]
（136+64）×（65-345÷23） (6.8-6.8×0.55)÷8.5
0.12× 4.8÷0.12×4.8 （58+37）÷（64-9×5）
812-700÷（9+31×11） （3.2×1.5+2.5）÷1.6
85+14×（14+208÷26） 120-36×4÷18+35
（284+16）×（512-8208÷18） 9.72×1.6-18.305÷7
4/7÷[1/3×（3/5-3/10）] （4/5+1/4）÷7/3+7/10
12.78－0÷（ 13.4＋156.6 ） 37.812-700÷（9+31×11） （136+64）×（65-345÷23） 3.2×（1.5+2.5）÷1.6
85+14×（14+208÷26） （58+37）÷（64-9×5）
(6.8-6.8×0.55)÷8.5 （284+16）×（512-8208÷18）
0.12× 4.8÷0.12×4.8 （3.2×1.5+2.5）÷1.6
120-36×4÷18+35 10.15-10.75×0.4-5.7
5.8×（3.87-0.13）+4.2×3.74 347+45×2-4160÷52
32.52-（6+9.728÷3.2）×2.5 87（58+37）÷（64-9×5）
[（7.1-5.6）×0.9-1.15] ÷2.5 （3.2×1.5+2.5）÷1.6
5.4÷[2.6×（3.7-2.9）+0.62] 12×6÷（12-7.2）-6
3.2×6+（1.5+2.5）÷1.6 （3.2×1.5+2.5）÷1.6
5.8×（3.87-0.13）+4.2×3.74
33.02－（148.4－90.85）÷2.5
（3）287×5+96990÷318 （4）1554÷[（72-58）×3]
Out of form calculation
2800÷ 100＋789 （947－599）＋76×64
1．36×(913－276÷23) 2．(93＋25×21)×9
3．507÷13×63＋498 4．723－(521＋504)÷25
5．384÷12＋23×371 6．(39－21)×(396÷6)
（1）156×[(17.7-7.2)÷3] （2）[37.85-（7.85+6.4）] ×30
（3）28×(5+969.9÷318) （4）81÷[（72-54）×9]
57×12－560÷35 848－640÷16×12
960÷（1500－32×45） [192－（54＋38）]×67
138×25×4 (13×125)×(3×8) (12+24+80)×50 704×25 25×32×125 32×(25+125)
178×101－178 84×36+64×84 75×99+2×75 83×102－83×2 98×199
123×18－123×3+85×123 50×(34×4)×3 25×（24+16） 178×99+178
79×42+79+79×57 7300÷25÷4 8100÷4÷75 75×27+19×2 5 31×870+13×310
4×(25×65+25×28) 138×25×4 (13×125)×(3×8) (12+24+80)×50
25×32×125 32×(25+125) 102×76 58×98
178×101－178 84×36+64×84 75×99+2×75 83×102－83×2
98×199 123×18－123×3+85×123 50×(34×4)×3 25×（24+16）
178×99+178 79×42+79+79×57 7300÷25÷4 8100÷4÷75
158+262+138
375+219+381+225
5001－247－1021－232
（181+2564）+2719
378+44+114+242+222
276+228+353+219
(375+1034)+(966+125)
(2130+783+270)+1017
99+999+9999+99999
7755－(2187+755)
2214+638+286
3065－738－1065
899+344
2357－183－317－357
2365－1086－214
497-299
2370+1995
3999+498
1883-398
12×25
75×24
138×25×4
(13×125)×(3×8)
(12+24+80)×50
704×25
25×32×125
32×(25+125)
88×125
102×76
58×98
178×101－178
84×36+64×84
75×99+2×75
83×102－83×2
98×199
123×18－123×3+85×123
50×(34×4)×3
25×（24+16）
178×99+178
79×42+79+79×57
7300÷25÷4
8100÷4÷75
16800÷120
30100÷2100
32000÷400
49700÷700
1248÷24
3150÷15
4800÷25
21500÷125
Additional questions:
2356－（1356－721）
1235－（1780－1665）
75×27+19×2 5
31×870+13×310
4×(25×65+25×28)
80+50+60+90+125
=130+150+125
=280+125
=405
Out of formula calculation: 360 △ [(12 + 6) × 5]
288÷[（26－14）×8]
500×6-(50×2-80)
（105×12－635）÷25
864÷[（27－23）×12]
（45＋38－16）×24
500－（240＋38×6）
[64－（87－42）] ×15
(845-15 × 3) △ 1612 × [(49-28) △ 7]... Expand
Out of formula calculation: 360 △ [(12 + 6) × 5]
288÷[（26－14）×8]
500×6-(50×2-80)
（105×12－635）÷25
864÷[（27－23）×12]
（45＋38－16）×24
500－（240＋38×6）
[64－（87－42）] ×15
（845－15×3）÷1612×[（49－28）÷7]
450÷[（84－48] ）÷12
（58+37）÷（64-9×5）
95÷（64-45）
178-145÷5×6+42
812-700÷（9+31×11）
85+14×（14+208÷26）
（284+16）×（512-8208÷18）
120-36×4÷18+35
（58+37）÷（64-9×5）
(6.8-6.8×0.55)÷8.5
0.12× 4.8÷0.12×4.8
（3.2×1.5+2.5）÷1.6
6-1.6÷4= 5.38+7.85-5.37=
7.2÷0.8-1.2×5= 6-1.19×3-0.43=
6.5×（4.8-1.2×4）=
5.8×（3.87-0.13）+4.2×3.74
32.52-（6+9.728÷3.2）×2.5
[（7.1-5.6）×0.9-1.15] ÷2.5
5.4÷[2.6×（3.7-2.9）+0.62]
12×6÷（12-7.2）-6
12×6÷7.2-6
0.68×1.9+0.32×1.9
（58+370）÷（64-45）
420+580-64×21÷28
（136+64）×（65-345÷23）
48.10.15-10.75 × 0.4-5.7
480*201+420*201
175*200+100-175
158+262+138
375+219+381+225
5001－247－1021－232
（181+2564）+2719
378+44+114+242+222
276+228+353+219
(375+1034)+(966+125)
(2130+783+270)+1017
99+999+9999+99999
Simple calculation of 100 ~ 150 fractions
Can be with scores Oh!
(0.5+x)+x=9.8÷2
2(X+X+0.5)=9.8
25000+x=6x
3200=450+5X+X
X-0.8X=6
12x-8x=4.8
7.5*2X=15
1.2x=81.6
x+5.6=9.4
x-0.7x=3.6
91÷x ＝1.3
X+8.3=10.7
15x ＝3
3x－8＝16
7(x-2)=2x+3
3x+9=27
18(x-2)=270
12x=300-4x
7x+5.3=7.4
3x÷5=4.8
30÷x+25=85
1.4×8-2x=6
6x-12.8×3=0.06
410-3x=170
3(x+0.5)=21
0.5x+8=43
6x-3x=18
1.5x+18=3x
5×3-x÷2=8
0.273÷x=0.35
1.8x=0.972
x÷0.756=90
9x-40=5
x÷5+9=21
48-27+5x=31
10.5+x+21=56
x+2x+18=78