Question 112700
{{{3x^2+11x-20=0}}}

{{{3x^2+15x-4x-20=0}}}

{{{3x(x+15)-4(x+5)=0}}}

{{{(3x-4)(x+5)=0}}}....well done up to here...

now, the product above will be equal to {{{0}}} if one or both factors are equal to {{{0}}}

let find out what are values for {{{x[1,2]}}}:

{{{3x - 4 = 0}}}

{{{3x = 4}}}

{{{x = 4/3}}}

if {{{x = 1.33}}}........first solution

{{{x + 5 = 0}}}

if {{{x = -5}}}.........second solution