How do I solve this equation? x^4 - 29x^2-100 = 0?

It's a quadratic in terms of x^2.

** Can you check that it's not meant to be x^4 - 29x^2 + 100 = 0 **

The given equation doesn't factor easily, and you get a really obscure answer. The amended equation becomes ...

(x^2 - 25)(x^2 - 4) = 0

(x + 5)(x - 5)(x + 2)(x - 2) = 0

x = -5, 5, -2, 2

... and this is more likely to be what the problem was about. I'll come back in an hour or so to see what's happening. :)

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<edit> Still, check the sign immediately before "100".

If y = x^2, then the equation can be written as:

y^2 - 29y (±) 100 = 0

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<edit 2> Okay, so it *is* y^2 - 29y + 100 = 0

Everything falls into place, as above.

Here's a handy reference – it covers the various methods of solving quadratics: http://www.purplemath.com/modules/solvquad.htm

The "index" page:

http://www.purplemath.com/modules/index.htm

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There is no reason to substitute. You know that x^2 * x^2 = x^4; and x * x = x^2

you also know that 25 * 4 = 100 and 25 + 4 = 29. Just pay attn to the signs.

so start with ( x^2 _ _ _ )(x^2 _ _ _ ) ; get the problem correct (lol)

and then ...............- 25...........- 4 .... and see if it works.

AFTER THIS, since 25 and 4 are both perfect squares, as is x^2

you can continue (x+5)(x-5)(x+2)(x-2)