a: =>(x+5)(4x-1+x-5)=0
=>(x+5)(5x-6)=0
=>x=-5 hoặc x=6/5
b: =>(x+7)(x-5)=0
=>x=5 hoặc x=-7
c: =>(2x+1)(x-2)(x+2)-(1-2x)(1+2x)(x+2)=0
=>(1+2x)(x+2)(x-2-1+2x)=0
=>(2x+1)(x+2)(3x-3)=0
=>\(x\in\left\{-\dfrac{1}{2};-2;1\right\}\)
d: =>(2x-1-x-3)(2x-1+x+3)=0
=>(x-4)(3x+2)=0
=>x=4 hoặc x=-2/3