Q12 of 20 Page 1

If the function f:R → R be given by f(x) = x2 + 2 and g :R → R be given by find fog and gof and hence find fog (2) and gof (– 3). [CBSE 2014]

f(x) = x2 + 2 and


let us find fog


⇒ fog = f(g(x))



Replace x by in f(x)



For fog(2) put x = 2



⇒ fog(2) = 6


Now let us find gof


⇒ gof = g(f(x))


⇒ gof = g(x2 + 2)


Replace x by x2 + 2 in g(x)




For gof(-3) put x = -3




Hence fog(2) = 6 and


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