Question

Question #77d22

Answer 1

`x=2 or x=-3/2`

Explanation:

We Have,
`f'(x)=-4/49`
Now `f (x)=1/ (4x-1)`
Differentiating with respect to `x` we get
`f'(x)=-1/((4x-1)^2)×4`
Now
`-1 /((4x-1)^2)×4=-4/49`
On solving we get
`x=2 or x=-3/2`

Answer 2

`x=-3/2" or "x=2`

Explanation:

`f(x)=1/(4x-1)=(4x-1)^-1`

`rArrf'(x)=-(4x-1)^-2xx4=-4/(4x-1)^2`

`rArr-4/(4x-1)^2=-4/49`

`rArr(4x-1)^2=49`

`rArrx=1/4+-7/4`

`rArrx=2" or "x=-3/2`