5x3 - 45x = 45x - 45x5x3 - 45x = 0.

Question

according to the solution i saw, it led to 5x(x^2-9)=0

Answer 1

the left side = 5x^3 -45x = 5x(x^2-9)=5x(x+3)(x-3) = 0

just factor out 5x

set each factor = 0, x=0,

x^2-9=0

x^2 =9

x = + or -3

x=-3, 0, or +3

middle terms though, 45x - 45x5x^3 -45x

= -45x5x^3

=-220x^4 =0

x=0

but odds are there's a mistake somewhere in that middle term "-45x5x^3" there's probably a missing + sign and it should read -45x + 5x^3, which factors into 5x(x^2-9)=0