Question

Ai giúp mình với

Bài 1 Thu gọn

A = ( x+3 ) ^2 - ( x + 2 ) ^2

B =( 2 x - 1 ) ( 2 x + 1 ) - ( 2x +3 ) ^2

Bài 2 tìm x
a ) x^2 + 2 x +1 =9

Answer 1

Bài 1: Thu gọn

a) Ta có: \(A=\left(x+3\right)^2-\left(x+2\right)^2\)

\(=\left[\left(x+3\right)-\left(x+2\right)\right]\cdot\left[\left(x+3\right)+\left(x+2\right)\right]\)

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

\(=2x+5\)

b) Ta có: \(B=\left(2x-1\right)\left(2x+1\right)-\left(2x+3\right)^2\)

\(=4x^2-1-\left(4x^2+12x+9\right)\)

\(=4x^2-1-4x^2-12x-9\)

\(=-12x-10\)

Bài 2: Tìm x

a) Ta có: \(x^2+2x+1=9\)

\(\Leftrightarrow\left(x+1\right)^2=9\)

\(\Leftrightarrow\left[{}\begin{matrix}x+1=3\\x+1=-3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-4\end{matrix}\right.\)

Vậy: \(x\in\left\{-4;2\right\}\)