Question

tìm x

(2x+1)(2x-1)-(2x-3)\(^2\)=-9

Answer 1

Lời giải:

$(2x+1)(2x-1)-(2x-3)^2=-9$

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

$\Leftrightarrow 4x^2-1-4x^2+12x-9=-9$

$\Leftrightarrow 12x-10=-9$
$\Leftrightarrow 12x=1$

$\Leftrightarrow x=\frac{1}{12}$

Answer 2

\(\left(2x-1\right)\left(2x+1\right)-\left(2x-3\right)^2=-9\)

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

\(\Leftrightarrow4x^2-1-4x^2+12x-9=-9\)

\(\Leftrightarrow12x-10=-9\)

\(\Leftrightarrow12x=1\)

\(\Leftrightarrow x=\dfrac{1}{12}\)

Vậy: \(x=\dfrac{1}{12}\)