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Quantitative Reasoning

Function notation — ISEE Upper practice questions

  • 37 questions on the paper
  • 70 practice questions in the app
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What this topic is

Function notation on the ISEE Upper Quantitative Reasoning section covers reading f(x) and related symbols, substituting a number for the input, and combining two functions.

A student has to evaluate a linear or quadratic rule at a stated value, compute a composition such as g of f of a number, and sometimes find a maximum of y on a closed interval. Questions are multiple-choice, and the choices are usually small integers.

Common traps include reversing composition order, treating the function as multiplication rather than substitution, and reporting a vertex that lies outside the given domain instead of checking the endpoints.

Sample questions

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Question 1Mid

What is the maximum value of yy if y=2x23y=2x^2-3 for 1x2-1\le x\le 2?

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Answer: C — 5

Since x2x^2 is largest at x=2x=2 on this interval, the maximum is 2(2)23=83=52(2)^2-3=8-3=5.

Question 2Easier

If f(x)=x23f(x)=x^2-3, what is the value of f(4)f(4)?

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Answer: C — 13

Substitute 4 for xx: f(4)=423=163=13f(4)=4^2-3=16-3=13.

Question 3Easier

If f(x)=x+4f(x)=x+4 and g(x)=x2g(x)=x^2, what is g(f(1))g(f(-1))?

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Answer: C — 9

Evaluate the inner function first: f(1)=1+4=3f(-1)=-1+4=3. Then g(f(1))=g(3)=32=9g(f(-1))=g(3)=3^2=9.

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