(4+2x)(5+2x)=56 ,+++--------+++--+

20+8x+10x+4x^2=56; 4x^2+18x+20-56=0; 4x^2+18x-36=0; 2x^2+9x-18=0; D=9^2-4*2*(-18)=81+144=225; x1=(-9-15)/4,x2=(-9+15)/4. x1= -6, x2=3/2.