a: \(\frac{2+3\left(x+5\right)}{8}>\frac{x-1}{4}\)
=>\(\frac{3x+15+2}{8}>\frac{2\left(x-1\right)}{8}\)
=>3x+17>2(x-1)
=>3x+17>2x-2
=>3x-2x>-2-17
=>x>-19
b: \(2x-x\left(2x+2\right)\le15-2x\left(x+2\right)\)
=>\(2x-2x^2-4x\le15-2x^2-4x\)
=>-2x<=15-4x
=>-2x+4x<=15
=>2x<=15
=>x<=15/2
c: ĐKXĐ: x∉{2;-2}
\(\frac{12}{x^2-4}-\frac{x+1}{x-2}+\frac{x+7}{x+2}=0\)
=>\(\frac{12-\left(x+1\right)\left(x+2\right)+\left(x+7\right)\left(x-2\right)}{\left(x-2\right)\left(x+2\right)}=0\)
=>12-(x+1)(x+2)+(x+7)(x-2)=0
=>\(12-\left(x^2+3x+2\right)+\left(x^2+5x-14\right)=0\)
=>\(12-x^2-3x-2+x^2+5x-14=0\)
=>2x-4=0
=>x=2(loại)
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