Solve by factoring $\displaystyle x^4-12x^2-64=0$ How? -.-
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Originally Posted by m0nkeysensei Solve by factoring $\displaystyle x^4-12x^2-64=0$ How? -.- Let $\displaystyle x^2=y$ Then you have: $\displaystyle y^2-12y-64=0$ $\displaystyle (y+4)(y-16)=0$ So, $\displaystyle (x^2+4)(x^2-16)=0$ $\displaystyle (x^2+4)(x+4)(x-4)=0$ $\displaystyle \therefore x=\pm 4$ and $\displaystyle x=\pm 2i$
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