2x4+4x6+6x8+.+98x100

Original formula = 2 * (1 * 2 + 2 * 3 +. + 49 * 50)
=2*(1*2+(2*3+3*4)+(4*5+5*6)+.+(48*49+49*50))
=2*(2*1^2+2*3^2+.2*49^2)
=4*(1^2+3^2+.49^2)
And 1 & sup2; + 3 & sup2; + 5 & sup2; + (2n-1) & sup2; = n (4N ^ 2-1) / 3
n=25
Then = 25 * (4 * 25 ^ 2-1) / 3 = 20825
Original formula = 83300

1. Wang Liang began to read a novel on January 5. If he read 80 pages a day and finished it on January 9, and if he read 90 pages a day and finished it on January 8, in order not to affect his normal study, Wang Liang prepared to reduce the amount of reading every day. He decided to finish it in a day. In this way, he would finish reading page a every day. How many pages does the novel have?
2. How many cuboid blocks do you need at least to stack a cuboid block of 9 cm long, 6 cm wide and 7 cm high into a cube?
3. The full score of a math exam is 100. The average score of six students in this exam is 91. The scores of these six students are different from each other. One of them only gets 65 points. So, how many points does the third student get at least?

According to the first condition, the number of pages is greater than 80 * 4 = 320 and less than 80 * 5 = 400. According to the second condition, the number of pages is greater than 90 * 3 = 270 and less than 90 * 4 = 360. Therefore, the total number of pages in the comprehensive upper book is between 320 and 260, with 324 pages. The least common multiple of 2.9, 6 and 7 is 126126 △ 9 = 14 (block) 126 △ 6 = 21 (block)

Put a pile of pieces into two boxes. The number of pieces in box a is 5 more than that in box B. If you take out 10 pieces in box a and put them into Box B, the number of pieces in box a is just half of that in box B. how many pieces are there in this pile?
I haven't learned the equation yet. Is there any other way?

Let a have X! So B has X-5!
2*（x-10）=x-5+10
x=25
So a has 15!
B has 20!

Factorization [(a-b) * 2 + 2 (B-A)] / (x + y)
[（a-b)²+2（b-a)]÷（x+y)
Is the answer A-B + 2 or a-b-2?
That's Square. Please tat

Should (x + y) be changed to (a-b) should be factorization [(a-b) ^ 2 + 2 (B-A)] / (a-b) [(a-b) ^ 2 + 2 (B-A)] / (a-b) = [(a-b) ^ 2-2 (a-b)] / (a-b) = [(a-b) ^ 2-2 (a-b)] / (a-b) = [(a-b) (a-b-2)] / (a-b) = a-b-2

4 (a + 2) ^ 2-12 (a + 2) (a + 3) + 9 (a + 3) ^ 2 factorization

4（a+2）^2-12（a+2）（a+3）+9（a+3）^2
=[2(a+2)]^2-2×2(a+2)×3(a+3)+[3(a+3)]^2
=[2(a+2)-3(a+3)]^2
=(-a-5)^2
=(a+5)^2

Factorization of quadratic trinomial
Factorize ax ^ 2 + BX + C (the formula contains a, B, c)

This is the root formula of a typical quadratic equation
If B & sup2; - 4ac ≥ 0, it can be decomposed into
a* (x-[-b+sqrt(b^2-4ac)]/2a)*
（ x-[-b+sqrt(b^2-4ac)]/2a)
Sqrt denotes the open root sign

When factoring a quadratic trinomial, student a misinterprets the coefficient of the first term and decomposes it into 2 (x-1) (X-9), while student B misinterprets the constant term and decomposes it into 2 (X-2) (x-4). Please judge the correct quadratic trinomial and decompose it correctly

2 (x-1) (X-9) = 2x2-20x + 18, 2 (X-2) (x-4) = 2x2-12x + 16; because student a misread the coefficient of the first term and student B misread the constant term, the correct quadratic trinomial is: 2x2-12x + 18; then factor it into 2x2-12x + 18 = 2 (x-3) 2

When factoring a quadratic trinomial, student a misread the coefficient of the first term
What student a misread is the coefficient of the first term, which is decomposed into (x + 9) (x + 1)
Student B misinterpreted the constant term and decomposed it into (x + 5) (x + 1)
Please factorize the quadratic trinomial correctly
QAQ

A (x + 9) (x + 1) = x & # 178; + 10x + 9
B (x + 5) (x + 1) = x & # 178; + 6x + 5
The first term coefficient is wrong
Student B misjudged the constant term
That's right: X & # 178; + 6x + 9 = (x + 3) &# 178;

Two students talk about the factorization of a quadratic trinomial. One student misinterprets the coefficient of a quadratic trinomial and decomposes it into two parts
Two students decompose a quadratic trinomial into a factor. One student decomposes it into 2 (x-1) (x-4) because he misread the coefficient of the first term, and the other student decomposes it into 2 (x + 2) (X-6) because he misread the constant term. After factoring the original polynomial, what is the correct result?

Restore and find out the correct one
If you misread an item once, it becomes:
2*（x^2-5x+4)
=2x^2-10x+8
There is only one wrong item and the rest is right
That is, the coefficient of quadratic term is 2 and the constant term is 8
alike:
Wrong constant term: wrong result:
=2*(x^2-4x-12)
=2x^2-8x-24
Then the quadratic term is 2 and the primary term is - 8
The correct formula is:
2x^2-8x+8
=2(x^2-4x+4)
=2(x-2)^2

There is a classical number reasoning problem in the civil service examination: 1,6,20,56144 () I don't understand,

6=1x2+4
20=6x2+8
56=2x20+16
144=2x56+32
(352)=2x144+64

2x4+4x6+6x8+.+98x100