The quadratic equation x^2 + 4kx+2(k+1) = 0 has equal roots, find the possible values of k.

For a quadratic equation ax^2 +bx +c = 0 with equal roots we know the discriminant b^2-4ac must equal 0. From our equation we have a=1, b=4k and c=2(k+1) so using b^2-4ac = 0 we have (4k)^2 -412(k+1) = 0 Expanding we get 16k^2-8k-8 = 0 Now we have a quadratic in k to solve, to make it easier we can start by dividing by 8 to give us 2k^2-k-1 = 0 Which factorises to (2k+1)(k-1) = 0 So we have 2k+1=0 and k-1=0 which gives us k=-1/2 and k=1 respectively. So these are our values of k that give the quadratic equation x^2+4kx+2(k+1) = 0 equal roots.

AA
Answered by Ayyub A. Maths tutor

31459 Views

See similar Maths A Level tutors

Related Maths A Level answers

All answers ▸

A curve f(x,y) is defined by sin(3y)+3ye^(-2x)+2x^2 = 5. Find dy/dx


Find the coordinates of the centre C and the length of the diameter of a circle with the equation (x-2)^2 + (y+5)^2 = 25


Solve for x, between 0 and 360 degrees, 4cos2 (x) + 7sin (x) – 2 = 0


(a) Express x +4x+7 in the form (x+ p) +q , where p and q are integers.


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:

© 2025 by IXL Learning