expressing x in terms of y, when y = x^2 + x - 1

Since x<sup>2</sup> + x - (1 + y) = 0, the Quadratic Formula might be a good place to start when attempting to find "x=".

Eliz.
 
I thought of using the quadratic formula but am not sure exactly what to do with it.
 
tdotgirl said:
I thought of using the quadratic formula but am not sure exactly what to do with it.
Click to expand...
"What to do with" the Quadratic Formula is simply the same things you've always done (though here with variables and numbers, rather than only numbers): Plug the given values into the Formula, and simplify. That's why I re-wrote your equation in Quadratic-Formula-ready formatting.

Or are you saying that you're not familiar with how the Formula works in the first place...?

Please reply with clarification, showing all of your work and reasoning so far. Thank you.

Eliz.
 
a = 1
b = 1
c = 1-y


x = [-1 +/- root(1 - 4(1)(1-y))] / 2(1)

= [-1 +/- root(1 - 4 - 4y)] / 2

= -1/2 +/- root(-3 - 4y) / 2


is that the right answer?
 
c = -(1+y), not (1-y)

you should get ...

\(\displaystyle \L x = \frac{-1 \pm \sqrt{4y + 5}}{2}\)
 
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