Algebrahard · Past Paper
Factorize completely: x^4 - 13x^2 + 36.
A(x-2)(x+2)(x-3)(x+3)
B(x^2-9)(x^2-4)
C(x-6)(x+6)(x-1)(x+1)
D(x-4)(x+4)(x-9)(x+9)
✓ Correct Answer: A — (x-2)(x+2)(x-3)(x+3)
Let y = x^2. y^2 - 13y + 36 = (y-9)(y-4) = (x^2-9)(x^2-4) = (x-3)(x+3)(x-2)(x+2).
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