Question

Find the value of m:
A. 7
B. 21
C. 15 or 14
D. none of these

Answer 1

given first eq is ,

x^2 + 10 x + 21 = 0

x^2 + 7 x + 3x + 21 = 0

x ( x + 7 ) + 3 ( x + 7 ) = 0

( x + 7 ) ( x + 3 ) = 0

x + 7 = 0 or x + 3 = 0

x = - 7 or x = - 3

putting these values one by one in second eq .

x^2 + 9 x + m = 0

(-7)^2 + 9 (-7) + m = 0

49 -63 + m = 0

m = 14


also

x^2 + 9 x + m = 0

(-3)^2 + 9 (-3) + m = 0

9 -27 + m = 0

m = 18

therefore m = 14 ---- from options