Quote:
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Originally Posted by Pip
Substitute (7x-2) with a ->
a^1/3 + (a+7)^1/3 = 3
(a+7)^1/3 = 3 - a^1/3
Raise both sides to the power of 3 ->
a+7 = 27 - 27a^1/3 + 9a^2/3 + a
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This is where I don't follow. When I cubed the right side I got the same thing you did, except - a instead of + a, so I get:
a+7 = 27 - 27a^1/3 + 9a^2/3 - a
Then I do b = a^(1/3) so I get:
a + 7 = 27 - 27b + 9b^2 - a
I'll be back, have to go turn something in...