How do you solve 2x^(2/5) - x(1/5) - 3 = 0 The answers are -1 or (243/32)?

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2007-09-19 12:32:01 · 2 answers · asked by Dalila 1 in Science & Mathematics ➔ Mathematics

2x^(2/5) - x(1/5) - 3 = 0
Let u = x(1/5)
2u^2 - u - 3 = 0
(2u - 3)(u + 1) = 0
u = 3/2, u = - 1
x = u^5
x = 343/32, - 1

2007-09-19 12:45:30 · answer #1 · answered by Helmut 7 · 1⤊ 1⤋

Helmut is correct, except for the final step.

u = 3/2 or u = -1
x = u^5, so...
x = (3/2)^5 = 243/32 or x = (-1)^5 = -1

2007-09-19 20:01:10 · answer #2 · answered by JM 4 · 0⤊ 0⤋