Question

*-5 is a root of the 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.* (CBSE 2014)

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Answer 1

Answer:

7/4

Step-by-step explanation:

-5 is a root of the given equation

thus substitute it in the given equation

$2( - 5) {}^{2} - 5p - 15 = 0$

$p = 7$

Form the Quadratic equation in the general form

$px {}^{2} + px + k = 0$

Substitute p

$7 {x}^{2} + 7x + k = 0$

Equal roots means D=0

$7 {}^{2} - 4(7)k = 0$

k=7/4

Answer 2

Answer:

Given root is -5 and for the equation 2x^2 + px - 15 = 0 possible roots are -5 and 6 because they had already given one root is -5

so the p value is 1 (p=1)

now sub p value in p(x^2+ x) + k = 0

we will get

x^2+x+k=0

sub x=-5

25-5+k=0

20+k=0

k=-20

please check the answer

and pre apologies if the answer is wrong