Differentiate, with respect to x, \(x^{3} + 2x\) from the first principle.

Assessment: WAEC SSCE - Further Mathematics - 2008 (Essay) Subject: Further Mathematics

Question 1 Report

Differentiate, with respect to x, \(x^{3} + 2x\) from the first principle.

Answer Details

Differentiate \(f(x)=x^3+2x\) from first principles.

By definition,

\[f'(x)=\lim_{h\to0}\frac{f(x+h)-f(x)}{h}.\]

Compute \(f(x+h):\)

\[f(x+h)=(x+h)^3+2(x+h)=x^3+3x^2h+3xh^2+h^3+2x+2h.\]

Then

\[f(x+h)-f(x)=3x^2h+3xh^2+h^3+2h.\]

Divide by \(h\) (for \(h\neq0\)):

\[\frac{f(x+h)-f(x)}{h}=3x^2+3xh+h^2+2.\]

Now let \(h\to0:\)

\[f'(x)=\lim_{h\to0}\left(3x^2+3xh+h^2+2\right)=3x^2+2.\]

Download The App On Google Playstore

Everything you need to excel in your exams

Green Bridge CBT Mobile App
Personalized AI Learning Chat Assistant
200,000+ Exam Questions Across IGCSE, JAMB, WAEC & NECO
Over 3,900 Lesson Notes
Offline Support - Learn Anytime, Anywhere
Green Bridge Timetable
Literature Summaries & Potential Questions
Track Your Performance & Progress
In-depth Explanations for Comprehensive Learning