\(A=3x-2y+\left\{x-\left(y+2x-5x-y\right)-8x+10y\right\}\)

\(=3x-2y+\left\{-7x+10y+3x\right\}\)

\(=3x-2y+10y-4x\)

=-x+8y

\(=-\left(a^2-2ab+b^2\right)+8\left(a^2+2ab+b^2\right)\)

\(=-a^2+2ab-b^2+8a^2+16ab+8b^2\)

\(=7a^2+18ab+7b^2\)

1, ?

2, ?

3, 4ab

Rút gọn

5x-3-|2x-1|

a: M+N-P

\(=7a^2-2a+1-a^2+4\)

\(=6a^2-2a+5\)

b: \(=2y-x-2x+y+y+3x-5y+x\)

\(=-3x+3y-4y+4x=x-y\)

\(=a^2+2ab+b^2-a^2+2ab-b^2=4ab\)

c: \(=\left[{}\begin{matrix}5x-3-2x+1=3x-2\left(x>=\dfrac{1}{2}\right)\\5x-3+2x-1=7x-4\left(x< \dfrac{1}{2}\right)\end{matrix}\right.\)

\(A=2y-x-\left\{2x-y-\left[y+3x-\left(5y-x\right)\right]\right\}\)

\(=2y-x-\left\{2x-y-\left[y+3x-5y+x\right]\right\}\)

\(=2y-x-\left\{2x-y-y-3x+5y-x\right\}\)

\(=2y-x-2x+y+y+3x-5y+x\)

\(=\left(2y+y+y-5y\right)+\left(-x-2x+3x+x\right)\)

= \(-y+x\)

Thay \(x=a^2+2ab+b^2,y=a^2-2ab+b^2\) vào đa thức -y + x :

\(-\left(a^2-2ab+b^2\right)+\left(a^2+2ab+b^2\right)\)

\(=-a^2+2ab-b^2+a^2+2ab+b^2\)

\(=\left(-a^2+a^2\right)+\left(2ab+2ab\right)+\left(-b^2+b^2\right)\)

= 4ab

\(A=2y-x-\left\{2x-y-\left[y+3x-\left(5y-x\right)\right]\right\}\\ =2y-x-\left\{2x-y-y-3x+5y-x\right\}\\ =2y-x-2x+y+y+3x-5y+x\\ =-y+x=-\left(a^2-2ab+b^2\right)+\left(a^2+2ab+b^2\right)\\ =-a^2+2ab-b^2+a^2+2ab+b^2=4ab\)