Question

3(x+5)-5(1-x)(1+x)=(x+3)^+(2x-1)^+13=Va rog.

Answer 1

$3(x+5)-5(1-x)(1+x)=(x+3)^2+(2x-1)^2+13 \\ 3x+15-5(1-x^2)=x^2+2 \cdot x \cdot 3+3^2+(2x)^2-2 \cdot 2x \cdot 1+1^2+13 \\ 3x+15-5+5x^2=x^2+6x+9+4x^2-4x+1+13 \\ 3x+5x^2-x^2-6x-4x^2+4x=9+1+13-15+5 \\ x=13$