Monday, February 15, 2016

If f(x) = 2x-3 and g(x) = x^2 -2 find fog(x) and gof(x).

f(x) = 2x-3


g(x) = x^2
-2


We need to find fog(x) and
gof(x).


We know that fog(x) =
f(g(x))


Then we will substitute with g(x) = x^2
-2


==> fog(x) = f( x^2 -2)


Now
we will substitute with x = x^2-x in f(x).


==> fog(x) =
2(x^2-2) -3


We will open
brackets.


==> fog(x) = 2x^2 -4
-3


==> fog(x) = 2x^2 -7


gof(x) =
g(f(x)) = g(2x-3) = (2x-3)^2 -2 = 4x^2 -12x + 9 -2 = 4x^2 -12x
+7


==> fog(x) = 2x^2 -7


==> gof(x) = 4x^2 -12x +
7

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