Question

Tìm x biết

a.x^2+8x+16=0

b.(x-1)^2+(2x+1)^2=(x+2)^2+(2x-1)^2

c.(2x+3)^2-(x+3)^2=0

Answer 1

a: \(x^2+8x+16=0\)

=>\(\left(x+4\right)^2=0\)

=>x+4=0

=>x=-4

b: \(\left(x-1\right)^2+\left(2x+1\right)^2=\left(x+2\right)^2+\left(2x-1\right)^2\)

=>\(x^2-2x+1+4x^2+4x+1=x^2+4x+4+4x^2-4x+1\)

=>2x+2=5

=>2x=3

=>\(x=\dfrac{3}{2}\)

c: \(\left(2x+3\right)^2-\left(x+3\right)^2=0\)

=>\(\left(2x+3+x+3\right)\left(2x+3-x-3\right)=0\)

=>\(x\left(3x+6\right)=0\)

=>3x(x+2)=0

=>x(x+2)=0

=>\(\left[{}\begin{matrix}x=0\\x+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-2\end{matrix}\right.\)