Given f(x)= 8 − x^2, solve f(3x) = -28

First substitute (3x) into the equation for f(x), giving f(3x) = 8 - 9x2. This is then equal to -28 and so it is remains to solve the equation 8 - 9x2 = -28. This can be written as 9x2 = 36, dividing through by 9 gives x2 = 4 and so x = ±2.

Related Further Mathematics GCSE answers

All answers ▸

Find the definite integral of f(x) = 12/(x^2+10x+21) with limits [-1,1]. Give your answer to 2 decimal places.


A curve has equation y = x^2 - 7x. P is a point on the curve, and the tangent to the curve at P has gradient 1. Work out the coordinates of P.


y=(6x^9 +x^8)/(2x^4), work out the value of d^2y/dx^2 when x=0.5


The circle c has equation x^2+ y ^2=1 . The line l has gradient 3 and intercepts the y axis at the point (0, 1). c and l intersect at two points. Find the co-ordinates of these points.


We're here to help

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