# Higher maths!!

Can someone help me with this differentiation question?

Calculate f’(4) given that f(x) = (2x^2 - 2) / root x

Sorry I couldn’t upload an image so it looks even more confusing written out. I thought the root x would have moved up to become -2x^-1/2
But all I know is the answer is 49/8 and I have no clue how to get that!! I thought differentiation was easy so I’m stressing
Original post by RaggaMuffin49
Can someone help me with this differentiation question?
Calculate f’(4) given that f(x) = (2x^2 - 2) / root x
Sorry I couldn’t upload an image so it looks even more confusing written out. I thought the root x would have moved up to become -2x^-1/2
But all I know is the answer is 49/8 and I have no clue how to get that!! I thought differentiation was easy so I’m stressing

I’m doing National 5 maths but from what I know,

For example if it says

F(x) = 3x + 7
Find the value of f(3)
You would then substitute the x for 3.
This means it would be
F(x)= 3(3) + 7
F(x)= 9 + 7
F(x)= 16

If however, it gives you an answer
For example if it says
F(x)=3x - 10
F(a)= -31. Find value of a
you would then do
3x - 10 = -31
(+10 to both sides)
3x = -21
(Divide by 3)
x= -7

Hope that helps, I have no clue how to do it if it’s not functions.
Original post by LSK104
I’m doing National 5 maths but from what I know,
For example if it says
F(x) = 3x + 7
Find the value of f(3)
You would then substitute the x for 3.
This means it would be
F(x)= 3(3) + 7
F(x)= 9 + 7
F(x)= 16
If however, it gives you an answer
For example if it says
F(x)=3x - 10
F(a)= -31. Find value of a
you would then do
3x - 10 = -31
(+10 to both sides)
3x = -21
(Divide by 3)
x= -7
Hope that helps, I have no clue how to do it if it’s not functions.

sadly that is not the answer as it involves the derivate of the function
where is this question from is it from a higher paper?
Original post by raggamuffin49
Can someone help me with this differentiation question?
Calculate f’(4) given that f(x) = (2x^2 - 2) / root x
Sorry I couldn’t upload an image so it looks even more confusing written out. I thought the root x would have moved up to become -2x^-1/2
But all I know is the answer is 49/8 and I have no clue how to get that!! I thought differentiation was easy so I’m stressing

Using index rules, when you divide by x^(1/2) you multiply (the whole numerator) by x^(-1/2), so use that to elminate the fraction and youre left with a relatively simple expression which can be differentiated as usual and then evaulate it when x=4.
(edited 2 months ago)
Original post by Blenxo
where is this question from is it from a higher paper?

It probably would have been a better idea to post the link originally instead of describe the q 😂
Original post by RaggaMuffin49
Can someone help me with this differentiation question?
Calculate f’(4) given that f(x) = (2x^2 - 2) / root x
Sorry I couldn’t upload an image so it looks even more confusing written out. I thought the root x would have moved up to become -2x^-1/2
But all I know is the answer is 49/8 and I have no clue how to get that!! I thought differentiation was easy so I’m stressing
If you find out I’d appreciate it! I’d say move the root x up to a power of a half, differentiate it so its 4x - x^-1/2, 4x4 is 16, 4 to the power of a -1/2 isn’t a whole number however so Im unsure how to continue to get 49/8! 49/16 is also not a whole number so Im unsure it they’ve times both numbers or not
Original post by RaggaMuffin49
Can someone help me with this differentiation question?
Calculate f’(4) given that f(x) = (2x^2 - 2) / root x
Sorry I couldn’t upload an image so it looks even more confusing written out. I thought the root x would have moved up to become -2x^-1/2
But all I know is the answer is 49/8 and I have no clue how to get that!! I thought differentiation was easy so I’m stressing

Separate f(x) into two fractions. (2x^2)/root x -2/root x . Simplify the indices and then proceed as normal with the differentiation then sub in x = 4 after differentiating.