Tìm x thuộc z:
\(a,\left(x^2+5\right)\left(x^2-25\right)=0\)
\(b,\left(x-2\right)\left(x+1\right)=0\)
\(c,\left(x^2+7\right)\left(x^2-49\right)< 0\)
\(d,\left(x^2-7\right)\left(x^2-49\right)< 0\)
\(e,\left(x-1\right)\left(x-2\right)\left(x^2+4\right)>0\)
GIÚP MIK VS, MIK CẦN GẤP