A curve C has the following equation: x^3 + 3y - 4(x^3)*(y^3) a) Show that (1,1) lies on C b) Find dy/dx

a) Substituting the coordinate (1,1) into the left hand side of the equation for C we obtain: (13) + 3*1 - 4(13)(13) = 1 + 3 - 4 = 0 = The right hand side of the equation, hence the equation is satisfied, and therefore (1,1) lies on C.

b) Differentiating implicity we find: 
3x2 + 3dy/dx - 12x2y- 12x3y2dy/dx = 0
Rearranging yields:
3x2 - 12x2y3= (12x3y2 - 3)dy/dx

Hence dy/dx = (3x2 - 12x2y3/(12x3y2 - 3)
Which simplifies to 

dy/dx = x2(1 - 4y3)/(4x3y2 - 1)

(An alternative expression can be obtained be moving the terms not involving dy/dx to the right hand side)

Answered by Harry W. Maths tutor

2800 Views

See similar Maths A Level tutors

Related Maths A Level answers

All answers ▸

Express x^2-4x+9 in the form (x-p)^2+q where p and q are integers


How can the trapezium rule be used to estimate a definite integral?


(i) Prove sin(θ)/cos(θ) + cos(θ)/sin(θ) = 2cosec(2θ) , (ii) draw draph of y = 2cosec(2θ) for 0<θ< 360°, (iii) solve to 1 d.p. : sin(θ)/cos(θ) + cos(θ)/sin(θ) = 3.


Solve the simultaneous equations: y-2x-4 = 0 (1) , 4x^2 +y^2 + 20x = 0 (2)


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences