SOLUTION: find the real solutions of the equation. x^(2/5)-3x^(1/5)-4=0

Click here to see ALL problems on real-numbers

Question 948047: find the real solutions of the equation. x^(2/5)-3x^(1/5)-4=0
Found 2 solutions by CubeyThePenguin, greenestamps:
Answer by CubeyThePenguin(3113) (Show Source):
You can put this solution on YOUR website!
Let x^(1/5) = b.

y^2 - 3y - 4 = 0
(y-4)(y+1) = 0

y = 4, y = -1

x^(1/5) = 4, x^(1/5) = -1

The "-1" solution is extraneous, so x = 4^5 = 1024.

Answer by greenestamps(13200) (Show Source):
You can put this solution on YOUR website!

And yet another hasty, careless, and incorrect response from tutor @CubeyThePenguin.

You can introduce a dummy variable, as he does in his response, to help solve the problem if you want; it is not necessary.

or
or

The x = -1 solution is NOT extraneous; it satisfies the original equation.