Answer:
x=√2, x=-√2, x= 3 and x=-3
Step-by-step explanation:
We need to solve the equation x^4 - 11x^2+18=0
We can replace x^4 = u^2 and x^2 = u
So, the equation will become
u^2 -11u+18 = 0
Factorizing the above equation:
u^2 -9u-2u+18 =0
u(u-9)-2(u-9)=0
(u-2)(u-9)=0
u=2, u=9
As, u = x^2, Putting back the value:
x^2 =2 , x^2 =9
taking square roots:
√x^2 =√2 ,√x^2=√9
x=±√2 , x = ±3
so, x=√2, x=-√2, x= 3 and x=-3
Answer:
Sol: In this question, firstly we have to make the first bracket as a complete square of the second bracket. This we can by adding 2.x.1/x which is equivalent to 2. Then the equation becomes:
6(x2 + 1/x2 +2) – 5(x + 1/x) = 50 { 38 + 6*2)
⇒ 6(x2 + 1/x2 +2) – 5(x + 1/x) – 50 = 0
Now put x + 1/x = y
⇒ 6y2 -5y -50 = 0
⇒ (2y +5)(3y-10)= 0
⇒ y=-5/2 or 10/3
As x is positive therefore, x + 1/x =10/3
On solving further you will get as x=3 or 1/3