If #f(x)=sqrtx#, #g(x)=7x+b# and #f(g(x))# passes through #(4,6)#, what is #b#?

Question

A #8#
B #26#
C #6#
D #4#

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Answer 1 · 2017-03-17T06:22:36

Answer is A.

As #f(x)=sqrtx# and #g(x)=7x+b#.

#y=f{g(x)}=sqrt(7x+b)#

As it passes through #(4, 6)#

#6=sqrt(7xx4+b)# and squaring both sides, we get

#36=28+b#

or #b=36-28=8#

Hence, answer is A.