What about 7, 9, 5, 9, 24

What about 7, 9, 5, 9, 24

1:(7 + 5 - 9) × 82:((7 + 5) - 9) × 83:(7 + (5 - 9)) × 84:(7 - 9 + 5) × 85:((7 - 9) + 5) × 86:(7 - (9 - 5)) × 87:8 × (7 + 5 - 9)8:8 × ((7 + 5) - 9)9:8 × (7 + (5 - 9))10:8 × (7 - 9 + 5)11:8 ×...

The known function is f (x) = 1 / √ (x ^ 2 + X + 1) (0

u=x^2+x+1(0

As shown in the picture, there is a zigzag road with a width of 2m on a grassland with a length of 20m and a width of 14m. Can you use your knowledge to calculate the green area of this grassland?

Translation makes the road straight. The road is a rectangle 20 m long and 2 m wide. The green area is 20 × 14-20 × 2 = 240 (M2). A: the green area of this grassland is 240 m2

1 * 3 of 2 + 1 * 5 of 2 + 1 * 2 of 2 (1 of 6 + 1 of 8) * 7 of 249 / 11 of 5 / 11 of 5 * 2 of 9

1 * 3 of 2 + 1 * 5 of 2 + 1 * 2 of 2
=1/2*（3+5+2）
=1/2*10
=5
(1 / 6 + 1 / 8) * 24
=1/6*24+1/8*24
=4+3
=7
7 of 9 / 11 of 5 + 5 of 11 * 2 of 9
=7/9*11/5+5/11*2/9
=（7/9+2/9）*5/11
=5/11

Given that the sequence {an} satisfies A1 = 0, A2 = 2 and belongs to n * for any m'n, there is a (2m-1) + a (2n + 1) = 2A (M + n-1) + 2 (m-n) ^ 2
Let CN = (a (n + 1) - an) Q ^ (n-1), find the first n terms and Sn of the sequence {CN}

a(2n-1)+a(2n+1)=2a(n+n-1)+0=2a(2n-1),
a(2n+1)=a(2n-1)=...=a(1)=0.
a(2n-1)=0.
a[2(n+1)-1] + a(2n+1) = 2a(n+1 + n-1) + 2(n+1-n)^2,
a(2n+1) + a(2n+1) = 0 = 2a(2n) + 2,
A (2n) = - 1, and a (2) = 2
There is something wrong with the title

A house is paved with square bricks. It needs 128 bricks with a side length of 3 decimeters. If it is replaced with square bricks with a side length of 2 decimeters, how many are needed? (using proportional knowledge)

Let's use 2-decimeter-long square bricks, which need x pieces, 2 × 2 × x = 3 × 3 × 128 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 4x = 1152 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & x = 288 A: use 2-decimeter-long square bricks, which need 288 pieces

5.125 - (3 and 1 / 2 + 3 / 8)

5.125 - (3 and 1 / 2 + 3 / 8)
=5 and 1 / 8-3 and 1 / 2-3 / 8
=41/8-3/8-7/2
=38/8-7/2
=(38-28)/8
=10/8
=5/4
=1.25

Sin α = 12 / 13 α ∈ (0, π / 2) cos β = - 3 / 5. Find sin (α + β) by β ∈ (π, 3 π / 2)

sinα=12/13
(sinα)^2+(cosα)^2=1
And α ∈ (0, π / 2)
So cos α > 0
cosα=5/13
cosβ=-3/5
(sinα)^2+(cosα)^2=1
And β∈ (π, 3 π / 2)
So sin β < 0
sinβ=-4/5
sin（α+β）=sinαcosβ+sinβcosα
=-56/65
It's pure hand fighting
If you don't understand, you can continue to ask

In triangle ABC, ∠ ACB = 90 ° quadrilateral CEDF is a square ad = 6bd = 4 to find the area of shadow part
See the space album on the picture

Let de = X,
∵DF ⊥AC,DE⊥BC
∴△ADF∽△DBE
BE/DF=4/6
∴BE=2/3x
∴BC=5/3x
Similarly, AC = 5 / 2x
(5/3x)^2+(5/2x)^2=AD^2=100
∴13x^2=144
The area of △ BDE = 1 / 2 × x × 2 / 3x = 1 / 3x ^ 2
Area of △ ADF = 1 / 2 × x × 3 / 2x = 3 / 4x ^ 2
Ψ shadow area = 1 / 3x ^ 2 + 3 / 4x ^ 2 = 13 / 12x ^ 2 = 144 × 1 / 12 = 12

If negative numbers a, B and C satisfy a + B + C = - 1, what is the maximum value of 1 / A + 1 / B + 1 / C

The title is equivalent to
If a, B, C are positive numbers and a + B + C = 1, what is the minimum value of 1 / A + 1 / B + 1 / C
The opposite of the number!
A+B+C=1,A>0 B>0C>0
1\A+1\B+1/C
=(A+B+C)/A+(A+B+C)/B+(A+B+C)/C
=1+B/A+C/A+1+A/B+C/B+1+A/C+B/C
=3 + B / A + A / B + C / A + A / C + C / B + B / C > = 3 + 6 = 9 basic inequality
The minimum value is 9
therefore
If negative numbers a, B, C satisfy a + B + C = - 1, then the maximum value of 1 / A + 1 / B + 1 / C is - 9