oquiella wrote:If the sum of the cubes of a and b is 8 and a6 - b6 = 14, what is the value of a3?
7/4
23/6
39/8
6
22/3
a� - b� = (a³ + b³)(a³ - b³).
Since a� - b� = 14 and a³ + b³ = 8, we get:
14 = 8(a³ - b³)
14/8 = a³ - b³.
7/4 = a³ - b³
Adding together a³ - b³ = 7/4 and a³ + b³ = 8, we get:
(a³ - b³) + (a³ + b³) = 7/4 + 8
2a³ = 39/4
a³ = 39/8.
The correct answer is
C.
Last edited by
GMATGuruNY on Fri Sep 04, 2015 9:53 am, edited 1 time in total.
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