Posted by Blair on Friday, February 15, 2013 at 12:11pm.
just make a substitution using, say, u to get a quadratic.
For example, in #6, let u = x^1/3 and you have
2u^2+5u-6=0
u = 1/4 (-5 ± √73)
Since u=x^1/3, x = u^3, so
x = 1/16 (-305 ± 37√73)
Kinda nasty, but straightforward.
How about #5? Let u=x^2-5, to get
2u^2 - 13u + 20 = 0
(u-4)(2u-5) = 0
so, u=4,5/2
That means
(x^2-5) = 4 or (x^2-5) = 5/2
x^2=9 or x^2 = 15/2
x = ±3 or ±√(15/2)
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