equations: solve x^4 - 4x^2 - 45 = 0

the quartic expression is quadratic in x^2 ... and it will factor

let u = x^2

now you have u^2 - 4u - 45 = 0

factor this, then back-substitute x^2 for u ... then finish factoring.
 
I don't know ... I haven't seen any of your work.

Get the hint?
 
I'm easier than Skeeter since he did most of the work. (Not that I don't think it would be a grand idea for you to show it too :evil: )

If
Is my answer then + - i to the square root of 5 and + - 3?
Click to expand...
means
Is my answer then + - i*sqrt(5) and + - 3?
Click to expand...
then yes, you are correct.
 
Thanks Gene;
to show my work I move the -6 to the other side and then I had:
(x+5)^2 =6
Then I took the square root of both side which is what our professor told us too.
then I got
x+5 = the square root of 6
then I subtracted five from both sides and ended up with x= -5 + - the square root of 6
 
??????????
That must be from another problem. This one was
(x²-9)(x²+5)=0

x²-9 = 0
x = +3 or

x²+5 = 0
x =+sqrt(-5)
 
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