Question

Tìm x, biết:

a) \(\left(3x-1\right)^2-\left(2x+3\right)^2=0\)

b)\(\left(12x-5\right)\left(4x-1\right)+\left(3x-7\right)\left(1-16x\right)=81\)

Answer 1

Giải:

a) \(\left(3x-1\right)^2-\left(2x+3\right)^2=0\)

\(\Leftrightarrow\left(3x-1+2x+3\right)\left(3x-1-2x-3\right)=0\)

\(\Leftrightarrow\left(5x+2\right)\left(x-4\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}5x+2=0\\x-4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{2}{5}\\x=4\end{matrix}\right.\)

Vậy ...

b) \(\left(12x-5\right)\left(4x-1\right)+\left(3x-7\right)\left(1-16x\right)=81\)

\(\Leftrightarrow48x^2-20x-12x+5+3x-7-48x^2+112x=81\)

\(\Leftrightarrow83x-2=81\)

\(\Leftrightarrow83x=83\)

\(\Leftrightarrow x=1\)

Vậy ...