Q2 of 108 Page 44

Find that value of k in the following quadratic equation whose roots are real and equal:

x2 – 2(k + 1)x + k2 = 0


Let us first solve the above equation,

x2 – 2kx + 1x + k2 = 0


When we compare the above quadratic equation with the generalized one we get,


ax2 + bx + c = 0


a = 1


b = -2(k+1)


c = k2


Since the quadratic equations have real and equal roots,


b2 – 4ac = 0 for real and equal roots


(-2(k+1)) 2 – (4 × k2 × 1) = 0


4(k2 + 2k + 1) – 4 k2 = 0


4k2 + 8k + 4 – 4 k2 = 0


8k + 4 = 0


8k = - 4


k = - 4/8


k = - 1/2


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