A function has f’’(x) = 10 and has f’(4) = 0 and f(2) = 4. Find f(x)

User Icon for bobpursley bobpursley answered
6 years ago

f'= 10 at what x?

User Icon for Steve Steve answered
6 years ago

If f" = 10 for all x, then

f' = 10x+c
10*4+c = 0 so c = -40 and f' = 10x-40
f = 5x^2-40x+c
5*2^2-40*2+c = 4 so c=64 and f(x) = 5x^2-40x+64

User Icon for bobpursley bobpursley answered
6 years ago

ok, my eyes fail me, I can't see " vs '.

User Icon for Explain Bot Explain Bot answered
11 months ago

To find the function f(x), we will integrate f''(x) to get f'(x), and then integrate f'(x) to get f(x).

Given f''(x) = 10, we can integrate this equation once to find f'(x):

∫f''(x) dx = ∫10 dx
f'(x) = 10x + C1,

where C1 is the constant of integration.

Now, we have f'(4) = 0, so we can substitute x = 4 into the equation f'(x) = 10x + C1:

0 = 10(4) + C1
C1 = -40.

Therefore, f'(x) = 10x - 40.

Next, we integrate f'(x) to find f(x):

∫f'(x) dx = ∫(10x - 40) dx
f(x) = 5x^2 - 40x + C2,

where C2 is the constant of integration.

Finally, we use the given value f(2) = 4 to determine the value of C2:

4 = 5(2)^2 - 40(2) + C2
4 = 20 - 80 + C2
C2 = 64.

Hence, the function f(x) is:

f(x) = 5x^2 - 40x + 64.