In the expansion of (x2 − 1x) 10, the term with the largest coefficient is () A. Item 6 B. items 6 and 7 C. items 4 and 6 D. items 5 and 7

In the expansion of (x2 − 1x) 10, the term with the largest coefficient is () A. Item 6 B. items 6 and 7 C. items 4 and 6 D. items 5 and 7

From tr + 1 = c10r (x2) 10-r (- 1x) r = (- 1) rc10r (x) 20-3r, we can see that the coefficient of each term in the expansion is (- 1) rc10r, and the coefficient is the largest. If and only if r = 4 or 6, the coefficient C104 of the fifth term is equal to the coefficient c106 of the seventh term, and the coefficient is the largest, so D

The coefficients of the expansion with x ^ 2 and x ^ 7 in (X-2) ^ 8

The general term t = CX ^ (8-r) * - 2 ^ R,
When r = 6, the coefficient of x ^ 2 = C (8,6) * 64 = 28 * 64 = 1792,
When r = 1, the coefficient of x ^ 7 term = C (8,1) * - 2 = - 16

(A / X - √ (x / 2)) ^ 9, where the coefficient of x ^ 3 is 9 / 4, find a

Because the power of X is 3,
Let the power of a / X be - 1 and the power of √ (x / 2) be 1 / 2
When expanding, if there are y first terms, then there are 9-y second terms,
Then (- 1) * y + 1 / 2 * (9-y) = 3
Then y = 1, x ^ 3 is multiplied by 1 A / X and 8 - √ (x / 2),
Then 9 * a * (1 / 2) ^ 8 = 9 / 4 (because any a / X is selected from 9, the front is multiplied by 9)
Then a = 64

(0.04x of 0.05 + 0.09) - (0.3x of 0.3 + 0.2) = 2 - (X-5 of 2) how to solve this equation
Remove the 2-in the following 2 - (...)

0.05 (0.04x + 0.09) - 0.3 (0.3x + 0.2) = 2 (X-5)
4/5x+9/5-x-2/3=1/2x-5/2
7/10x=109/30
x=109/21

The formula method is used to solve the following equation

2 / 2x-3x-5 = 0
X squared-6x-10 = 0
X squared - 6x + 9 = 19
(x-3) square = 19
X-3 = ± root 19
X = 3 ± root 19
X1 = 3 + radical 19, X2 = 3 - radical 19

1. If X-2 / x-3 and 3x + 2 / 2-x are reciprocal, find the value 2 of X and solve the equation about X: x-a / x + X + B / a = 1 (a ≠ 0)

3-x=3x+2,x=1/4
ax-a^2=2x+b
a=2,b=4.
When a is not equal to 2, x = (B + A ^ 2) / (A-2)

Check that the following numbers are solutions to the equation 3x + 2 = 5
x=-1 x=1
Write down what the process should be

3x+2=5
3x=5-2
3x=3
x=1

Consult experts --- solve the equation and test: (1) 3x-7 = 2; (2) - 1 / 3x = 3
(Note: 1 / 3 is one third)

3x-7=2
3x=2+7
3x=9
x=3
-1 / 3x = 3 multiply both sides by - 3 to get
x=-9

The solution equation: (1) half x + third x = 1 (2) x + Half X-1 = 3 (3) half (2x-1) + one third (2x-1) = five sixths
（4）x-2x+3x-4x+...+99x-100x=25

(1) Two thirds x + three thirds x = 1 multiply by 6
3x+2x=6
5x=6
x=6/5
(2) X + Half X-1 = 3
1.5x=3+1
1.5x=4
x=40/15
x=8/3
(3) 1 / 2 (2x-1) + 1 / 3 (2x-1) = 5 / 6 times 6
3（2x-1）+2(2x-1)=5
6x-3+4x-2=5
6x+4x=5+5
10x=10
x=1
（4）x-2x+3x-4x+...+99x-100x=25
-x-x-...-x=25
-50x=25
x=-1/2

How to solve the equation 3x ^ 2-16x-35 = 0

3x^2-16X-35=0
(x-7)(3x+5)=0
x1=7 x2=-5/3