Q11 of 82 Page 4

For what value of k does the quadratic equation

4 x2 - 2(k +1) x +(k + 4) = 0 have equal roots? (CBSE 2013)

 


For a quadratic equation, ax2 + bx + c = 0,


D = b2 – 4ac


If D = 0, roots are real and equal



⇒ D = 4(k + 1)2 – 4 × 4(k + 4) = 0


⇒ 4k2 + 8k + 4 – 16k – 64 = 0


⇒ k2 – 2k - 15 = 0


⇒ k2 – 5k + 3k – 15 = 0


⇒ (k – 5)(k + 3) = 0


⇒ k = -3, 5

More from this chapter

All 82 →
9

Find the value(s) of k so that the quadratic equation 3x2 – 2kx + 12 = 0 has equal roots? (CBSE 2012)

 10

For what value of k does the quadratic equation

(k – 12) x2 + 2(k – 12) x +2 = 0 have equal roots? (CBSE 2013)

 12

For what value of k does the quadratic equation

kx (x – 2√5) + 10 = 0 have equal roots? (CBSE 2013)

 13

For what value of k does the quadratic equation

(k +4) x2 + (k +1) x +1 = 0 have equal roots? (CBSE 2013)