Need help

I'm currently trying hard to complete some required math classes so I can goto university. However, studying from home is extremely difficult due to the fact that the book doesn't explain shit.

Are there any good sites that explain the chapter in my book called "Algebra and Functions" in an understandable way for someone who is studying from home?

Right now I'm stuck on some equations that look sort of like this:

 Solve the equation x^4 + 6x^2 - 40 = 0
 by setting x^2 = t

I checked the end of the book where all the aswers are posted and according to that:
First  x = 2
Second x = -2

How does that calculation work?

t^2 + 6t - 40 = 0
(t - 4)(t + 10) = 0
t = 4, -10
t = x^2
x = sqrt(t)
x = 2, -2, and two complex numbers

I dont understand how t = 4, -10 can become x = 2, -2 when sqrt(t)

Is the second x just automatically -2 ?

also, my calculator wont sqrt(-10)

I've probably just missed something really basic, I know, but that needs to be fixed, right? I can't stay a newbie forever. :)

t = 4 gives x = 2 or -2. This is because 2 and -2 both square to give 4.

t = -10 gives no real solutions for x, because no real numbers square to give -10.

Thank you for helping!

I might get stuck again in the future, so I hope it's okay that I ask the allmighty wisdom of Anonymous once in a while. You could be helping a fellow Anon reach the high end of education.

>>5

Something in me doubts it...

>>6

Ouch...