A curve with equation y=f(x) passes through the point (1, 4/3). Given that f'(x) = x^3 + 2*x^0.5 + 8, find f(x).

We know that f'(x) = x^3 + 2*x^0.5 + 8, and we can integrate both sides. This gives us f(x) = (1/4)*x^4 + (4/3)x^(3/2) + 8x + c, remembering to add the constant of integration. Now, we are almost there, but we need to use the first bit of information from the question. The curve y=f(x) passes through (1, 4/3), so when x=1, y=4/3. This is the same as saying that when x=1, f(x)=4/3, i.e. f(1)=4/3. But we know that f(1)= (1/4)*1^4 + (4/3)1^(3/2) + 81 + c, from before (just put 1 instead of x), so setting this equal to 4/3 gives: 1/4 + 4/3 + 8 + c = 4/3, 1/4 + 8 + c = 0, 33/4 + c = 0, c = -33/4. So f(x) = (1/4)*x^4 + (4/3)x^(3/2) + 8x - 33/4.

GC
Answered by George C. Maths tutor

6965 Views

See similar Maths A Level tutors

Related Maths A Level answers

All answers ▸

Write cosx - 3sinx in the form Rcos(x + a)


Find the general solution of the differential equation: d^2x/dt^2 + 5dx/dt + 6x = 2cos(t) - sin(t)


Find the equation of the tangent to the curve y = 4x^2 (x+3)^5 at the point (-1, 128).


Find ∫ (2x^5 - 1/(4x^3)-5) dx. giving each term in its simplest form.


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

MyTutor is part of the IXL family of brands:

© 2026 by IXL Learning