Factorise :
x4 - 5x2 - 36
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= x4 - (9 - 4)x2 - 36
= x4 - 9x2 + 4x2 - 36
= (x4 - 9x2) + (4x2 - 36)
= x2(x2 - 9) + 4(x2 - 9)
= (x2 - 9)(x2 + 4)
= ((x)2 - (3)2)(x2 + 4)
= (x - 3)(x + 3)(x2 + 4)
Hence, x4 - 5x2 - 36 = (x - 3)(x + 3)(x2 + 4)
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25(a - 5b)2 - 4(a - 3b)2
a2 - 0.36 b2
15(2x - y)2 - 16(2x - y) - 15
Evaluate (using factors) : 3012 x 300 - 3003