To factor 125x3 + 64 ,
use the form a3 + b3 = (a + b)(a2 - ab + b2),
where here "a" is "5x" and "b" is "4", to get:
125x3 + 64 = (5x + 4)[(5x)2 - (5x)(4) + 42]
125x3 + 64 = (5x + 4)(25x2 - 20x + 16).
No more factoring is possible.
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