SOLUTION: I am having a hard time solving this equation quadratic in form: 9x(to the 4th power)=85x(squared)-196. I know it then becomes 9x(to the 4th power)-85x(squared)+196=0. Then u =

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: I am having a hard time solving this equation quadratic in form: 9x(to the 4th power)=85x(squared)-196. I know it then becomes 9x(to the 4th power)-85x(squared)+196=0. Then u =      Log On


   

Question 570835: I am having a hard time solving this equation quadratic in form:
9x(to the 4th power)=85x(squared)-196.
I know it then becomes 9x(to the 4th power)-85x(squared)+196=0.
Then u = x squared. So then it becomes 9u squared-85u+196=0
Now I'm stuck on how to solve the equation from here because I don't think I factor here???
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
9x%5E4-85x%5E2%2B196=0
u=x^2
9u%5E2-85u%2B196=0
In such problems you can solve by quadratic formula or completing the squares

9u%5E2-85u%2B%2885%2F6%29%5E2=+-196+%2B+%2885%2F6%29%5E2
9u%5E2-85u%2B%2885%2F6%29%5E2=+-196+%2B+%287225%2F36%29

%283u-%2885%2F6%29%29%5E2=%28-7056%2B7225%29%2F%2836%29

3u-85%2F6%29%5E2=%28169%2F36%29
Take the square root on both sides
3u-85/6 = -/-(13/6)
3u=85/6 + 13/6
3u=98/6
u=98/18
OR
3u= 85/6 -13/6
3u=72/6
u=72/18
u=4
when u = 4 , x=+/-2
when u=98/18 =====> 49/9===>x=sqrt(49/9)====>+/- 7/3
m.ananth@hotmail.ca