Đáp án: a.$x\in\{-1,3\}$
b.$x=-\dfrac{4423}{325}$
Giải thích các bước giải:
a.Ta có:
$(x-3)(x+1)=0\to x-3=0\to x=3$
Hoặc $x+1=0\to x=-1$
b.Ta có :
$\dfrac{x+1}{12}+\dfrac{x+2}{11}+\dfrac{x+22}{9}+\dfrac{x+23}{8}=0$
$\to \dfrac{x+1}{12}\cdot \:792+\dfrac{x+2}{11}\cdot \:792+\dfrac{x+22}{9}\cdot \:792+\dfrac{x+23}{8}\cdot \:792=0\cdot \:792$
$\to 66\left(x+1\right)+72\left(x+2\right)+88\left(x+22\right)+99\left(x+23\right)=0$
$\to 66x+66+72x+144+88x+1936+99x+2277=0$
$\to 325x+4423=0$
$\to 325x=-4423$
$\to x=-\dfrac{4423}{325}$
