\(x^4-16=\left(x^2\right)^2-4^2=\left(x^2-4\right)\left(x^2+4\right)=\left(x-2\right)\left(x+2\right)\left(x^2+4\right)\)
\(x^2-64=x^2-8^2=\left(x-8\right)\left(x+8\right)\)
\(x^4-16=\left(x^2\right)^2-4^2=\left(x^2-4\right)\left(x^2+4\right)=\left(x-2\right)\left(x+2\right)\left(x^2+4\right)\\ x^2-64=x^2-8^2=\left(x-8\right)\left(x+8\right)\)
x4-16=(x2)2-42=(x2+4)(x2-4)
x2-64=x2-82=(x+8)(x-8)