20xsquared+40 x+15=0
factor out 5
u get
5(4x^2+8x +3) = 0
5(4x^2+2x+6x+3)=0
5(2x(2x+1)+3(2x+1))=0
5(2x+1)(2x+3)=0
x=-1/2
or
x=-3/2
u get
5(4x^2+8x +3) = 0
5(4x^2+2x+6x+3)=0
5(2x(2x+1)+3(2x+1))=0
5(2x+1)(2x+3)=0
x=-1/2
or
x=-3/2