Ta có
x4 + 64
<=> x4 + 64 -16x2 + 16x2
<=> (x4 + 16x2 + 64 ) - 16x
<=> (x2 + 8)2 - (4x)2
<=> (x2 + 8 - 4x ) (x2 + 8 + 4x)
x4+64
=(x2)2+82
=(x2)2+2.8.x2+82 -2.8.x2(về hằng đẳng thức)
=(x2+8)2-16x2
=(x2+8)2-(4x)2
=(x2+8-4x)(x2+8+4x)
x^4+64
= x^4+6a+16x^2-16x^2
= (x^4+16x^2+64)-(4x)^2
= (x-8)^2-(4x)^2
= (x-8-4x)(x-8+4x)
= (-3x-8)(5x-8)
\(x^4+64\)
\(=\left(x^2\right)^2+8^2\)
= \(\left(x^2+8\right)\left(x^2-8\right)\)