Question

(x²-4)²+2(x²+5)² = 66

Answer 1

$(x^2-4)^2+2(x^2+5)^2=66 \\ \\ x^4-8x^2+16+2(x^4+10x^2+25)=66 \\ \\ x^4-8x^2+16+2x^4+20x^2+50=66 \\ \\ 3x^4+12x^2=0 \\ \\ y=x^2 \\ \\ 3y^2+12y=0 \\ \\ 3y(y+4)=0 \\ \\ y_1=0 \\ \\ y_2=-4$
Logo x=0