Đáp án: a.$ x=-\dfrac73$
b.$x\in\{-\dfrac17,\dfrac32\}$
c.$x=-3$
Giải thích các bước giải:
a.$3x-1-5(x+2)=x-4$
$\to -2x-11=x-4$
$\to -3x=7$
$\to x=-\dfrac73$
b.$(5x-2)(3-2x)=4x^2-9$
$\to 5\cdot \:3x-5\cdot \:2xx-2\cdot \:3+2\cdot \:2x=4x^2-9$
$\to -10x^2+19x-6=4x^2-9$
$\to -14x^2+19x+3=0$
$\to -14x^2-2x+21x+3=0$
$\to -2x(7x+1)+3(7x+1)=0$
$\to (-2x+3)(7x+1)=0$
$\to x\in\{-\dfrac17,\dfrac32\}$
c.ĐKXĐ: $x\ne \pm2$
Ta có:
$\dfrac1{x+2}-\dfrac{3}{x-2}=\dfrac{4x+10}{x^2-4}$
$\to\dfrac1{x+2}-\dfrac{3}{x-2}=\dfrac{4x+10}{(x-2)(x+2)}$
$\to \dfrac{1}{x+2}\left(x+2\right)\left(x-2\right)-\dfrac{3}{x-2}\left(x+2\right)\left(x-2\right)=\dfrac{4x+10}{(x-2)(x+2)}\left(x+2\right)\left(x-2\right)$
$\to x-2-3\left(x+2\right)=2\left(2x+5\right)$
$\to -2x-8=4x+10$
$\to -6x=18$
$\to x=-3$
