Question 570835
{{{9x^4-85x^2+196=0}}}

u=x^2

{{{9u^2-85u+196=0}}}
In such problems you can solve by quadratic formula or completing the squares


{{{9u^2-85u+(85/6)^2= -196 + (85/6)^2}}}

{{{9u^2-85u+(85/6)^2= -196 + (7225/36)}}}


{{{(3u-(85/6))^2=(-7056+7225)/(36)}}}


{{{3u-85/6)^2=(169/36)}}}

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