SOLUTION: .4 x = 81 its x to the 4th power = 81 I don't know if I'm doing it right (x^+9)(x^-9)=0 (x+3)(x-3)(x+3)(x-3)=0 x-3=0 x=3 x+3=0 x=-3 (3,-3)

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: .4 x = 81 its x to the 4th power = 81 I don't know if I'm doing it right (x^+9)(x^-9)=0 (x+3)(x-3)(x+3)(x-3)=0 x-3=0 x=3 x+3=0 x=-3 (3,-3)       Log On


   

Question 144534: .4
x = 81
its x to the 4th power = 81
I don't know if I'm doing it right
(x^+9)(x^-9)=0
(x+3)(x-3)(x+3)(x-3)=0
x-3=0 x=3
x+3=0 x=-3
(3,-3)
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
There are 4 4th roots. You show 2 of them.
There are 2 square roots of 81, 9 and -9. Each of these has 2 square roots. 3 and -3 are the square roots of +9.
The other 2:
x%5E2+=+-9
x%5E2%2B9=0
Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)
Quadratic equation ax%5E2%2Bbx%2Bc=0 (in our case 1x%5E2%2B0x%2B9+=+0) has the following solutons:

x%5B12%5D+=+%28b%2B-sqrt%28+b%5E2-4ac+%29%29%2F2%5Ca

For these solutions to exist, the discriminant b%5E2-4ac should not be a negative number.

First, we need to compute the discriminant b%5E2-4ac: b%5E2-4ac=%280%29%5E2-4%2A1%2A9=-36.

The discriminant -36 is less than zero. That means that there are no solutions among real numbers.

If you are a student of advanced school algebra and are aware about imaginary numbers, read on.


In the field of imaginary numbers, the square root of -36 is + or - sqrt%28+36%29+=+6.

The solution is x%5B12%5D+=+%28-0%2B-i%2Asqrt%28+-36+%29%29%2F2%5C1+=++%28-0%2B-i%2A6%29%2F2%5C1+, or
Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+1%2Ax%5E2%2B0%2Ax%2B9+%29