(x+4)((x^2) - kx - 5) is expanded and simplified. The coefficient of the x^2 term twice the coefficient of the x term. Work out the value of k.

(x + 4) (x2 - kx - 5) = x3 - kx2 - 5x + 4x2 - 4kx - 20 = x3 + (4-k)x2 + (-5-4k)x - 20.The coefficients are: (4-k) of x2 and (-5-4k) of x. Now we can write the equation:(4-k) = 2(-5 - 4k) /expand4 - k = -10 - 8k /+8k4 + 7k = -10 /-47k = -14 /divide by 7k = -2

Related Further Mathematics GCSE answers

All answers ▸

Find the tangent to the equation y=x^2 -2x +4 when x=2


Prove that tan^2(x)=1/(cos^2(x))-1


Lengths of two sides of the triangle and the angle between them are known. Find the length of the third side and the area of the triangle.


If the equation of a curve is x^2 + 9x + 8 = y, then differentiate it.


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