ISEE Upper Level Mathematics Achievement Quiz: Function Rules From Data

What this quiz covers

This quiz focuses on Function Rules From Data, giving you a quick way to practice the rules, question types, and explanations that matter most for ISEE Upper Level Mathematics Achievement.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. $g(x) = 3x - 2$
2. $g(x) = x^2 - 2x + 3$ (correct answer)
3. $g(x) = 2^x + x - 2$
4. $g(x) = \frac{x^3 - x}{2} + 2$

Explanation: Testing each function with the given points: For g(x) = x² - 2x + 3: g(1) = 1 - 2 + 3 = 2, g(2) = 4 - 4 + 3 = 3, g(3) = 9 - 6 + 3 = 6, g(4) = 16 - 8 + 3 = 11. All values match. Choice A gives g(3) = 7, not 6. Choice C gives g(3) = 8 + 3 - 2 = 9, not 6. Choice D gives g(3) = 13, not 6.

Question 2

1. $h(x) = -\frac{2}{3}x + \frac{16}{3}$ (correct answer)
2. $h(x) = -\frac{3}{2}x + 7$
3. $h(x) = \frac{2}{3}x + \frac{2}{3}$
4. $h(x) = -\frac{1}{2}x + 5$

Explanation: From the graph, when x = 2, h(x) = 4, and when x = 5, h(x) = 2. The slope is (2-4)/(5-2) = -2/3. Using point-slope form with (2,4): h(x) - 4 = -2/3(x - 2), so h(x) = -2/3x + 4/3 + 4 = -2/3x + 16/3. Choice B has the wrong slope. Choice C has positive slope. Choice D uses slope -1/2 instead of -2/3.

Question 3

1. 2
2. 3 (correct answer)
3. 4
4. 5

Explanation: To find f⁻¹(8), we need to find the x-value where f(x) = 8. From the graph, f(3) = 8, so f⁻¹(8) = 3. Alternatively, since f and f⁻¹ are reflections across y = x, the point (8,3) on f⁻¹ corresponds to (3,8) on f. Choice A corresponds to f⁻¹(6). Choice C corresponds to f⁻¹(10). Choice D corresponds to f⁻¹(12).

Question 4

1. 47
2. 51 (correct answer)
3. 55
4. 59

Explanation: When you encounter a recursive sequence problem, you need to carefully identify the pattern and apply it step by step to find the desired term. This sequence follows the rule: each term after the first two equals the sum of the two preceding terms, multiplied by 2, minus 1. Mathematically, this is $a_n = 2(a_{n-1} + a_{n-2}) - 1$ for $n \geq 3$. Starting with $a_1 = 1$ and $a_2 = 3$, let's calculate each subsequent term: For $a_3$: $a_3 = 2(a_2 + a_1) - 1 = 2(3 + 1) - 1 = 2(4) - 1 = 7$ For $a_4$: $a_4 = 2(a_3 + a_2) - 1 = 2(7 + 3) - 1 = 2(10) - 1 = 19$ For $a_5$: $a_5 = 2(a_4 + a_3) - 1 = 2(19 + 7) - 1 = 2(26) - 1 = 51$ Therefore, $a_5 = 51$, which is choice B. Choice A (47) might result from forgetting to subtract 1 in the final calculation. Choice C (55) could come from adding 1 instead of subtracting 1 in the recursive formula. Choice D (59) might occur if you forgot the "minus 1" part entirely and just used $a_n = 2(a_{n-1} + a_{n-2})$. For recursive sequence problems, always write out each step methodically rather than trying to jump ahead. Double-check your arithmetic at each stage, and make sure you're applying the exact formula given—small details like "minus 1" are crucial and often where test-makers place traps.

Question 5

1. 82 (correct answer)
2. 86
3. 94
4. 106

Explanation: When you encounter a recursive function like this, you're working with a formula that defines each output in terms of a previous output. The key is to apply the given relationship step-by-step, starting from the known value. Given that $f(x+1) = 3f(x) - 2$ and $f(0) = 4$, you need to find $f(3)$ by calculating $f(1)$, then $f(2)$, then $f(3)$. Start with $f(1)$: Using $x = 0$ in the formula gives $f(0+1) = 3f(0) - 2$, so $f(1) = 3(4) - 2 = 12 - 2 = 10$. Next, find $f(2)$: Using $x = 1$ gives $f(1+1) = 3f(1) - 2$, so $f(2) = 3(10) - 2 = 30 - 2 = 28$. Finally, find $f(3)$: Using $x = 2$ gives $f(2+1) = 3f(2) - 2$, so $f(3) = 3(28) - 2 = 84 - 2 = 82$. Choice A (82) is correct. Choice B (86) likely comes from adding 2 instead of subtracting it in the final step: $3(28) + 2 = 86$. Choice C (94) might result from miscalculating $f(2)$ as 32 instead of 28, then computing $3(32) - 2 = 94$. Choice D (106) could come from forgetting to subtract 2 entirely in multiple steps or other arithmetic errors. For recursive function problems, always work systematically from the given starting point. Double-check each calculation before moving to the next step, since errors compound quickly in sequential computations.

Question 6

1. $p(n) = 2n^2 + n + 3$
2. $p(n) = n^2 + 3n + 3$
3. $p(n) = 2n^2 + 2n + 3$ (correct answer)
4. $p(n) = n^2 + 4n + 3$

Explanation: When you encounter a recursive function definition, you need to find an explicit formula that produces the same values. The best approach is to test each given formula against the known values and the recursive pattern. Let's verify the correct formula by checking $p(n) = 2n^2 + 2n + 3$ against our initial conditions:

• $p(0) = 2(0)^2 + 2(0) + 3 = 3$ ✓
• $p(1) = 2(1)^2 + 2(1) + 3 = 7$ ✓

• Using recursion: $p(2) = 2p(1) - p(0) + 4 = 2(7) - 3 + 4 = 15$
• Using formula: $p(2) = 2(4) + 4 + 3 = 15$ ✓

Question 7

1. 127 (correct answer)
2. 135
3. 143
4. 151

Explanation: When you encounter a sequence problem like this, your goal is to identify the underlying pattern by examining how the function values change from one input to the next. Let's look at the given values: $f(1) = 3$, $f(2) = 7$, $f(3) = 15$, $f(4) = 31$. First, calculate the differences between consecutive terms: $7 - 3 = 4$, $15 - 7 = 8$, $31 - 15 = 16$. The differences are 4, 8, 16 — each difference doubles! This suggests the pattern follows $f(x) = 2^{x+1} - 1$. Let's verify: $f(1) = 2^2 - 1 = 3$ ✓, $f(2) = 2^3 - 1 = 7$ ✓, $f(3) = 2^4 - 1 = 15$ ✓, $f(4) = 2^5 - 1 = 31$ ✓. Now we can find $f(6) = 2^7 - 1 = 128 - 1 = 127$. We also need $f(5) = 2^6 - 1 = 63$ to continue the sequence. Answer A (127) is correct. Answer B (135) might result from incorrectly adding 32 twice to get from $f(4)$ to $f(6)$, missing that the differences themselves increase. Answer C (143) could come from assuming a constant second difference without recognizing the doubling pattern. Answer D (151) might result from misapplying an arithmetic progression with too large a common difference. Strategy tip: For sequence problems, always examine first differences, then second differences if needed. Look for patterns like doubling, squaring, or adding consecutive integers — these frequently appear on standardized tests.

Question 8

1. $\frac{2}{3}$ (correct answer)
2. $\frac{3}{4}$
3. $\frac{4}{3}$
4. $\frac{5}{3}$

Explanation: The average rate of change from x = 1 to x = 4 is [f(4) - f(1)]/(4 - 1). From the graph, f(1) = 2 and f(4) = 4. Therefore, the average rate of change is (4 - 2)/(4 - 1) = 2/3. Choice B uses the wrong endpoint values. Choice C inverts the fraction. Choice D uses f(4) = 7 instead of 4.

Question 9

1. 8
2. 12
3. 16 (correct answer)
4. 20

Explanation: For a quadratic function q(x) = ax² + bx + c, we have q(1) = a + b + c. From the table, q(1) = 16. Therefore, a + b + c = 16. Choice A assumes q(0) gives a + b + c. Choice B uses the average of the given values. Choice D uses q(2) incorrectly.

Question 10

1. Linear function with positive slope
2. Quadratic function with positive leading coefficient
3. Exponential function with base greater than 1 (correct answer)
4. Logarithmic function with positive coefficient

Explanation: Examining the ratios between consecutive outputs: 6/2 = 3, 18/6 = 3, 54/18 = 3, 162/54 = 3. Since the ratio is constant, this indicates an exponential function. The function appears to be f(x) = 2 × 3^(x-1). Choice A would show constant differences. Choice B would show constant second differences. Choice D would show decreasing differences that approach zero.