d: =>5x(x-3)=0
=>x=0 hoặc x=3
e: =>3x(x-4)(x+4)=0
hay \(x\in\left\{0;4;-4\right\}\)
f: \(\Leftrightarrow5x\left(x^2+4\right)=0\)
hay x=0
g: \(\Leftrightarrow x^2+8x-x-8=0\)
=>(x+8)(x-1)=0
=>x=-8 hoặc x=1
h: \(\Leftrightarrow\left(x-11\right)\left(x+1\right)=0\)
hay \(x\in\left\{11;-1\right\}\)
a, Ta có : \(5x-9=0\Leftrightarrow x=\dfrac{9}{5}\)
b, \(x^2-7x=0\Leftrightarrow x\left(x-7\right)=0\Leftrightarrow x=0;x=7\)
c, \(2x^2+12x=0\Leftrightarrow2x\left(x+6\right)=0\Leftrightarrow x=-3;x=0\)
d, \(5x^2-15x=0\Leftrightarrow5x\left(x-3\right)=0\Leftrightarrow x=0;x=3\)
e, \(3x^3-48x=0\Leftrightarrow3x\left(x^2-16\right)=0\Leftrightarrow3x\left(x-4\right)\left(x+4\right)=0\Leftrightarrow x=0;x=-4;x=4\)
f, \(5x^3+20x=0\Leftrightarrow5x\left(x^2+4>0\right)=0\Leftrightarrow x=0\)
g, \(x^2+8x-x-8=0\Leftrightarrow x\left(x+8\right)-\left(x+8\right)=0\Leftrightarrow\left(x-1\right)\left(x+8\right)=0\Leftrightarrow x=-8;x=1\)
h, \(x^2-11x+x-11=0\Leftrightarrow x\left(x+1\right)-11\left(x+1\right)=0\Leftrightarrow\left(x-11\right)\left(x+1\right)=0\Leftrightarrow x=-1;x=11\)