Re: stupid, stupid quadratics.

Posted by T.Gracken on September 13, 2002 at 08:55:41:

In Reply to: stupid, stupid quadratics. posted by tony on September 13, 2002 at 04:46:14:

:
: okay, i know how to do regular quadratic equations, with the standard ax2 +/- bx +/- c. here's the probmem posed. x2 + 3x + (radical)x2 + 3x(end radical) = 6 here is what i'm doing, please tell me what i'm doing wrong. okay, to get rid of the radical, i square both sides. so it results in x4 + 9x2 + x2 + 3x = 36, and thus, x4 + 10x2 + 3x = 36. so i have three different exponential values for x.. one to the fourth power, one to the second, and one w/o an exponent. what do i do?

first, use "^" to indicate an exponent. for example, x^2 means "x squared". second, use sqrt( ) for a square root. for example sqrt(2) means square root of 2.

now, you might try substituting a letter in place of a bunch of symbols.

For instance, suppose you let A = sqrt(x²+3x)

then notice that A² = x²+3x

now rewrite the problem using A and A² to get

A² + A = 6

I'll bet you can solve that for A. Then "back substitute". that is, once you get A = a number, replace the A with sqrt(x²+3x) and solve that equation.

you can also use this technique to solve other equations that have "quadratic forms". for example, try letting A = 1/(x+1) in the next problem you wrote.

see if that helps.

: also.. i have one more that i need help with.
: ___1___ = __1__ + 2
: (x+1)2 = x+1

: oh yeah.. this is the last one. promise.
: 3x^-2 - 7x^-1 - 6 = 0
: (thus, 3x to the -2 power minus 7x to the -1 power, etc)

: help!

: -tony

Follow Ups:

• Re: stupid, stupid quadratics. Dennis Borris 15:32:27 09/13/02 (3)
  • Re: stupid, stupid quadratics. T.Gracken 09:52:59 09/16/02 (0)
  • Y ...... (n/t) Subhotosh Khan 16:02:56 09/13/02 (0)
  • I didn't post that; you around, Dr See ? Denis Borris 16:01:40 09/13/02 (0)

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