(X^2-49)^2+(x^2+4x-21)^2=0

[latex](x^2-49)^2+(x^2+4x-21)^2=0\\(x-7)^2(x+7)^2+(x^2+7x-3x-21)^2=0\\(x-7)^2(x+7)^2+(x(x-3)+7(x-3))^2=0\\(x-7)^2(x+7)^2+(x+7)^2(x-3)^2=0\\(x+7)^2((x-7)^2+(x-3)^2)=0\\\\x+7=0\\x=-7;\\\\(x-7)^2+(x-3)^2=0\\x^2-14x+49+x^2-6x+9=0\\2x^2-20x+58=0|:2\\x^2-10x+29=0\\D: \; 100-116=-16\ \textless \ 0.[/latex]