• May 23rd 2007, 03:27 PM
shortd333
okay, i have this question and i have to find the roots/x-intercepts/zeros w/e of -4xsquared+5x+7 and i can't figure it out because the answer using the quadratic formula is different then the ones given (its multiple choice) can anyone help me? ... i dont know if this makes any sense though ...
• May 23rd 2007, 03:39 PM
Jhevon
Quote:

Originally Posted by shortd333
okay, i have this question and i have to find the roots/x-intercepts/zeros w/e of -4xsquared+5x+7 and i can't figure it out because the answer using the quadratic formula is different then the ones given (its multiple choice) can anyone help me? ... i dont know if this makes any sense though ...

Let's try the quadratic formula one more time:

$-4x^2 + 5x + 7 = 0$

$\Rightarrow x = \frac {-5 \pm \sqrt {5^2 - 4(-4)(7)}}{2(-4)}$
$\Rightarrow x = \frac {-5 \pm \sqrt {137}}{-8}$
$\Rightarrow x = \frac {5}{8} \pm \frac { \sqrt {137}}{8}$