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Re: f(x) = x2 + 1 g(x) = x – 2
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26 Mar 2018, 18:49
This is a function problem involving nested functions. An easy way of thinking of functions is as though they're a find and replace in a word processing document. For example, if f(x) = x^2 + 2x + 1, then when they give you f(2), you can simply replace every x you see with a 2, giving you 2^2 + 2x2 + 1 = 9.
In quantity A and B they've given us nested functions, one inside the other. In cases like these, simply do the inside one first, then the outside one next. Since quantity A is f(g(–1)), let's do g(-1) first. Since g(x) = x - 2, we can substitute x for -1, giving us -1 - 2 = -3. Now we plug -3 into the outside function, which is f(x) = x^2 + 1, giving us (-3)^2 + 1 = 10.
Let's do the same for quantity B, in which the inside function is f(x). So we'll plug -1 into f(x) first, and then the result into g(x) next. Plugging -1 into x^2 + 1 gives us (-1)^2 + 1 = 2, and plugging 2 into x - 2 gives us 2 - 2 = 0.
Since quantity A gives us 10 and quantity B gives us 0, the answer is A.