if -5 is a root of the quadratic 2x^2+kx-15=0 and quadratic eqation k(x^2+x)+p^=0 has eqal roots find value of p
Answers
Answer:Since -5 is a root of the given quadratic equation it will make the polynomial equal to zero. Hence, in place of x , we can put -5 i. e. x = -5
Now , f(x) = 2x²+ kx - 15 =0
f(-5) = 2(-5)² +k(-5) - 15 =0
= 50 - 5k - 15 = 0
= 35 - 5k = 0
= -5k = - 35
= k = 7
Now , f(x) = k(x² + x) + p = 0
f(-5) = k[(-5)² +(-5) ] + p =0
Putting value of k in the equation = 7[(-5)²+(-5)] + p =0
= 7 (20) +p = 0
= p = -140
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