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Re: Graph of the function f in the xy-plane [#permalink]
14 Dec 2015, 05:59

1

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Expert's post

Solution

Here we have a functions whose values are defined Graphically.

We need to compute the value of \(f(f(-1))\). To do so we need to find the value of \(f(-1)\) first. Now looking up the value from the graph we see that \(f(-1)= 2\).

Hence the problem is reduced to finding the value of \(f(2)\). Again from the graph we see that \(f(2) = 1\).

Thus \(f(f(-1))=1\).
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Re: Graph of the function f in the xy-plane [#permalink]
25 Jul 2017, 23:57

So my understanding is - in case we have these kind of functions say f(f(f(f(-2) (say based on above graph) we keep substituting the innermost value of f? Please do let me know. thank you!

Re: Graph of the function f in the xy-plane [#permalink]
26 Jul 2017, 06:24

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TUTTIAM52 wrote:

Could anyone explain more in detail why the solution is D. I am lost.

We evaluate the brackets first. So we find the value of \(f(-1)\) from the graph \(f(-1)=2\). So putting the value of \(f(-1)\) in \(f(f(-1))=f(2)\).

Now we look up tha value of \(f(2)\) from the graph

nancyjose wrote:

So my understanding is - in case we have these kind of functions say f(f(f(f(-2) (say based on above graph) we keep substituting the innermost value of f? Please do let me know. thank you!

Yes you are right!
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Sandy If you found this post useful, please let me know by pressing the Kudos Button

Many people struggle with function notation. However, it's really just the same as the "y = some expression with x" notation you've seen before (e.g., y = 3x + 1)

So, for example, asking for the value of f(-1) is the same as asking "What the value of y is when x = -1?"

When we look at the given graph we see that the point (-1, 2) lies ON the graph. So, we can say "when x = -1, y = 2"

This is exactly the same as saying f(-1) = 2

Now that f(f(-1)) = f(2), what is the value of f(2)? This is the same as asking "What's the value of y when x = 2?"

When we look at the given graph we see that the point (2, 1) lies ON the graph. So, we can say "when x = 2, y = 1"