Expert: Bobby Soltani - 9/3/2004

Question
Solve the equation by any convenient method.

80+6x=9x2

(eighty plus six x equals 9x squared)

Answer
Hi Suzy,

80+6x = 9x^2
9x^2 - 6x - 80 = 0

you can use the quadratic equation.
(-b + SQRT(b^2-4ac))/(2a) and (-b - SQRT(b^2-4ac))/(2a)
where our a=9, b=-6, and c = -80

First, I'll solve the SQRT part.

SQRT((-6)^2 - 4*9*(-80)) = 54

for the first equation we have:
(6+54)/(2*9) = 60/18 = 10/3
for the second equation, we have:
(6-54)/(2*9) = -48/18 = -24/9 = -8/3

That's it.  Let me know if you have questions.

Bobby