Question

find the value of k for which the equation x²-kx-21=0 and x²-3kx+35=0 have a common root
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Answer 1

Step-by-step explanation:

x²-kx-21=0

x²-3kx+35=0

2kx=14

kx=7

or

x²-kx-21=0

alpha +beta =k

alpha beta =-21

x²-3kx+35=0

alpha + beta =3k

alpha. beta =35

k=35

3k=21

k=7