Factorise the following:
7a3 + 56b3
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7a3 + 56b3 = 7(a3 + 8b3)
= 7[(a)3 + (2b)3]
We know that,
a3 + b3 = (a + b)(a2 - ab + b2)
∴ 7[(a)3 + (2b)3] = 7(a + 2b)[a2 - a.2b + (2b)2]
= 7(a + 2b)(a2 - 2ab + 4b2).
Hence, 7a3 + 56b3 = 7(a + 2b)(a2 - 2ab + 4b2).
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64x3 + 1