Question

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

Answer 1

Answer:

k = -140

Explanation:

-5 is a root of quadratic equation.

Therefore, x = -5

2x^2+px-15=0 (putting x = -5)

2X(-5)^2 + pX(-5) - 15 = 0

(2X25) - 5p - 15 = 0

50 - 5p - 15 = 0

-5p + 35 = 0

-5p = -35

p = -35/-5

p = 7

now,

p(x^2+x) +k = 0 ( put x = -5 & p = 7)

7 [(-5^2) + (-5)] + k = 0

7 (25-5) +k = 0

7 X 20 + k = 0

140 + k = 0

k = -140