# If — 5 is a root of the quadratic equation 2x2 + 2px — 15 = 0 and the quadratic equation p (x2 + x) + k = 0 has equal roots, find the value of k.

2x2 + 2px — 15 = 0

Put x = –5

2(–5)2 + 2p(–5) — 15 = 0

50 – 10p – 15 = 0

35 = 10p

p = 3.5

Equation p (x2 + x) + k = 0 has equal roots i.e. d = 0

p (x2 + x) + k = 0

p = 3.5

3.5 (x2 + x) + k = 0

3.5x2 + 3.5x + k = 0

d = b2 – 4ac

d = (3.5)2 – 4(3.5)(k)

d = 12.25 – 14k

Putting d = 0

Equation will be:

0 = 12.25 – 14k

14k = 12.25

k = 0.875

Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos
Quiz | Knowing the Nature of Roots44 mins
Take a Dip Into Quadratic graphs32 mins
Foundation | Practice Important Questions for Foundation54 mins
Nature of Roots of Quadratic Equations51 mins
Getting Familiar with Nature of Roots of Quadratic Equations51 mins
Quadratic Equation: Previous Year NTSE Questions32 mins
Champ Quiz | Quadratic Equation33 mins
Balance the Chemical Equations49 mins
Understand The Concept of Quadratic Equation45 mins
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation
view all courses