2x(x-3)-(x+1)(x+2)=(x-3)^2
2x^2-6x-(x^2+2x+x+2)=x^2-2*3x+3^2
2x^2-6x-x^2-3x-2=x^2-6x+9
-3x=11
x=-\frac{11}{3}
sprawdzenie
L=2*(-\frac{11}{3})[(-\frac{11}{3})-3]-[(-\frac{11}{3})+1]*[(-\frac{11}{3})+2]=(-\frac{22}{3})(-\frac{20}{3})-(-\frac{8}{3})(-\frac{5}{3})=\frac{440}{9}-\frac{40}{9}=\frac{400}{9}=44\frac{4}{9}
P=[(-\frac{11}{3})-3]^2=(\frac{20}{3})^2=\frac{400}{9}=44\frac{4}{9}
L=P