It is known that: x-xy = 20, xy-y = 12, then X-Y =..., - 2XY + X + y =

It is known that: x-xy = 20, xy-y = 12, then X-Y =..., - 2XY + X + y =

x-xy=20 ①
xy-y=12 ②
① + 2
x-y=32
① - 2
-2xy+x+y=8

Simplify x ^ 2 + XY / X △ XY + y ^ 2 / 2XY

It can be found that x 2 - 2XY + y 2 is exactly the complete square formula by observing the molecule, and then it can be factorized by the square difference formula
(x-y)2-1
x-y-1
=
(x-y+1)(x-y-1)
x-y-1
=x-y+1．
Comments: when completing this kind of simplification, we should first decompose the part of the numerator and denominator that can decompose the factor. Some need to extract the common factor first, while some need to use the formula method to decompose the factor. By decomposing the factor, we can decompose the part of the numerator and denominator that can decompose the factor into the form of product, and then find the common factor

For the equation x2-mx-1 = 0 of X, if the absolute value of the difference is 3, then the value of M is?

Let two be x1, x2;
The result shows that it is > 0;
And (x1-x2) 2 = 9,
That is, (x1 + x2) 2-4x1x2 = 9;
Substituting: M2 = 5
m=+-5

If the absolute value of the difference between the two equations x2 + MX-15 = 0 is 8, find the value of M______ ．

∵ equation x2 + MX-15 = 0, quadratic coefficient a = 1, primary coefficient b = m, constant term C = - 15, ∵ X1 + x2 = - m, x1 · x2 = - 15, and ∵ equation x2 + MX-15 = 0, the absolute value of the difference between the two is 8, ∵ x1-x2 | = 8, ∵ x1-x2 (x1-x2) 2 = 64, ∵ X1 + x2) 2-4x1 · x2 = 64, ∵ (- M) 2-4 × (- 15) = 64, that is M2 + 60 = 64, the solution is m = ± 2

Teacher's composition of human beings

Nature is the teacher of human beings, cactus, ants, these natural things can be seen everywhere, so they are not uncommon, but you can not underestimate them. Have you ever seen a group of small ants crawling on the wall, they always carry small food like sand, walking in groups

Solution equation: (160 + 4x) - 3x = 160 + X

（160+4X）—3X=160+X
160+4x-3x=160+x
x=x
X can be any value
If you still don't understand, you can continue to ask (^ o ^)/~

3.33 * 7 + 9.99

3.33X7+9.99
=3.33X7+3.33X3
=3.33X10
=33.3
Weng Jinwen answers for you,
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Shandong Education Press Volume 3 mathematics with you to learn the answer
With your ability to learn P37, the challenge is urgent!

7. Choose B
8. Set up C department, and the number of civil servants left is X
150/84+56+60=x/60
x=45
Answer... (omitted)
I've found this book for you. I hope it's the answer you want

If the price of a commodity is m yuan after two consecutive price reductions of 10%, then the price of the commodity is m yuan

M÷【（1-10%）×（1-10%）】
=M÷0.81
=100M / 81 yuan
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Given the function FX = ln ax + 1 + 1-x / 1 + X, X ≥ 0, where a > 0, find the monotone interval 2 of 1.fx
If the minimum value of FX is 1, find the value range of A

Given the function f (x) = ln (AX + 1) + (1-x) / (1 + x), x > = 0, where a > 0, (1) find the monotone interval of F (x) (2) if the minimum value of F (x) is 1, find the value range of A
f′(x)=[a/(a+1)]-[2/(1+x)²]
=(ax²+a-2)/(ax+1)(1+x)²
∵x≥0
a>0
∴ax+1>0
① When a ≥ 2
On the interval (0, + ∞), f ′ (x) > 0
② When 0 √ [(2-A) / a]
From F '(x)