Question

please solve using quadratic formula:
2r^2=9r+81

Answer 1

Write the quadratic formula here

Answer 2

-b±√ ̅ b^2-4ac
_______________
2a

Answer 3

apply the formula, and write what you got

Answer 4

1) -9±√ ̅ 9^2-4*2*81
_______________
2*2
2)-9±√ ̅ 12474
_______________
4
but then i get a realy big decimal

Answer 5

what am i doing wrong?

Answer 6

here is your mistake..

Make the equation =0 not as it is now.

This will give you the equation....
\[2r^2-9r-81=0\]
from here do the formula.
\[\frac{ 9\pm \sqrt{(-9)^2-4(2)(-81)}}{ 4} \]
\[\frac{ 9\pm \sqrt{729} }{ 4 }\]
\[=\frac{ 9\pm27 }{ 4}\]

Answer 7

ooooohh duhh stupid mistake lol thank you so much!!

Answer 8

no problem