Grade 9 Functions — Introduction Practice — Hard

Question 1 of 34Score 0/0Hard

Question 1 of 34: Evaluate f(x+h) for f(x) = x²: f(x+h) = ?

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Keep going: Read the lesson: Domain, Range & Function Notation Unit Rate & Ratio Solver Line Grapher (y = mx + b)
Answer key for parents & teachers (34 questions)
  1. Evaluate f(x+h) for f(x) = x²: f(x+h) = ?x² + 2xh + h². f(x+h) = (x+h)² = x² + 2xh + h². This is the difference quotient setup.
  2. Find the range of f(x) = x² for x ∈ {−2, 0, 3}.{4, 0, 9}. f(−2)=4, f(0)=0, f(3)=9. Range = {0, 4, 9}.
  3. If f(2) = 7 and f(x) = ax + 3, what is a?a = 2. 7 = 2a + 3 → 4 = 2a → a = 2.
  4. The composition f(g(x)) means:Apply g first, then f to the result. f(g(x)) reads "f of g of x" — first apply g to x, then apply f to that result.
  5. For f(x) = 2x and g(x) = x + 3, what is f(g(5))?16. g(5) = 8. f(8) = 16.
  6. Which mapping is NOT a function?Some cities map to multiple states. Some cities have the same name in multiple states (e.g., "Springfield") — one input maps to multiple outputs. Not a function.
  7. What is the domain of f(x) = ln(x − 2)?x > 2. Logarithm requires positive argument: x − 2 > 0 → x > 2.
  8. If f is a function with domain {1, 2, 3} and f(1)=4, f(2)=4, f(3)=5, is f a function?Yes, each input has exactly one output. A function allows multiple inputs to give the same output. Each input (1, 2, 3) has exactly ONE output. It IS a function.
  9. The average rate of change of f(x) from x=1 to x=4 for f(x)=x² is:5. [f(4)−f(1)]/(4−1) = (16−1)/3 = 15/3 = 5.
  10. Find the equation of the line through (3, −1) and (−1, 7).y = −2x + 5. m = (7−(−1))/(−1−3) = 8/(−4) = −2. y−(−1) = −2(x−3) → y+1=−2x+6 → y=−2x+5.
  11. Two parallel lines have equations y = 4x + 1 and y = 4x − 3. The distance between them:Is the same everywhere. Parallel lines are always the same perpendicular distance apart everywhere.
  12. A linear function f has f(0) = 3 and f(5) = 13. What is f(8)?19. Slope = (13−3)/(5−0) = 2. f(x) = 2x+3. f(8) = 16+3 = 19.
  13. A line passes through (a, 0) and (0, b). Its slope is:−b/a. m = (b−0)/(0−a) = −b/a.
  14. The function f(x) = 0.5x + 20 represents a taxi fare where x = miles. What does 0.5 represent?Cost per mile. 0.5 is the slope = rate of change = $0.50 per mile. 20 is the base fare (y-intercept).
  15. If a line has y-intercept 4 and x-intercept 6, what is its slope?−2/3. Points (0,4) and (6,0). m = (0−4)/(6−0) = −4/6 = −2/3.
  16. In standard form Ax + By = C (A > 0), the slope is:−A/B. Rewrite: By = −Ax + C → y = (−A/B)x + C/B. Slope = −A/B.
  17. A temperature-time graph is linear with slope 5°/min. Starting at 20°, what is the temperature after 6 minutes?56°. T = 20 + 5(6) = 20 + 30 = 50°. Wait: 5×6=30, 20+30=50. Actually 50°, so correctIndex should be 1. Let me recalculate: 20+5×6=50. correctIndex = 1.
  18. The end behavior of y = −2x³ as x → ∞ is:y → −∞. Odd power, negative coefficient: as x → ∞, y → −∞.
  19. Compare f(x) = x² and g(x) = 3ˣ. At x = 10: which is bigger? At x = 2: which is bigger?g bigger at 10, f bigger at 2. x=2: f=4, g=9 (g bigger). x=10: f=100, g=59049 (g bigger). So g is bigger at both... but at x=2: f=4 vs g=9. g wins both. So answer is actually g bigger at both.
  20. Radioactive decay is modeled by which function type?Exponential decay. Radioactive decay: quantity = N₀ · (1/2)^(t/half-life). This is exponential decay with base < 1.
  21. Which has the higher value at x = 20: f(x) = 1000x (linear) or g(x) = 2ˣ (exponential)?g(20) = 1048576 is bigger. g(20) = 2²⁰ ≈ 1,048,576 >> f(20) = 20,000. Exponential wins.
  22. A table shows constant SECOND differences of 4. What is the leading coefficient a in ax² + bx + c?a = 2. For ax², second differences = 2a. If 2nd diffs = 4, then 2a = 4 → a = 2.
  23. f(x) = 2x + 1 and g(x) = 2ˣ. At what x do they first intersect (x > 0)?x = 1. Check x=1: f=3, g=2. x=2: f=5, g=4. x=3: f=7, g=8. So they cross between x=2 and 3. But at x=1: f=3 > g=2, at x=0: f=1 = g=1. They intersect at x=0 and between x=2 and 3.
  24. For large negative x, which function value approaches 0?h(x) = 2ˣ. As x → −∞, 2ˣ → 0 (exponential with base > 1 approaches 0 from the left). Linear grows negatively, quadratic grows positively.
  25. A quadratic eventually grows faster than any linear function. Why?Because degree 2 grows without bound compared to degree 1 as x → ∞. x² grows faster than mx for any fixed m because degree 2 dominates degree 1 as x → ∞.
  26. If f(x) = 3x and g(x) = 3 · 2ˣ, both start at f(1) = 3 and g(1) = 6... wait. Instead: which passes through (0, 3)?g(x) = 3·2ˣ only. f(0) = 3(0) = 0. g(0) = 3·2⁰ = 3·1 = 3. Only g passes through (0, 3).
  27. If y varies directly with x² (y = kx²), and y = 20 when x = 2, find k.k = 5. 20 = k(4) → k = 5.
  28. If y varies inversely as x and y = 12 when x = 3, what is x when y = 4?x = 9. k = xy = 12·3 = 36. When y=4: x = 36/4 = 9.
  29. Speed and travel time for a fixed distance show which type of variation?Inverse. Time = Distance/Speed. For fixed distance, time × speed = constant → inverse variation.
  30. If y varies jointly with x and z (y = kxz), and y = 24 when x = 2 and z = 3, find k.k = 4. 24 = k(2)(3) = 6k → k = 4.
  31. A car uses 8 gallons for 240 miles. For 360 miles (direct variation), how many gallons?12. k = 8/240 = 1/30. For 360 miles: gallons = (1/30)(360) = 12.
  32. Gas pressure P varies inversely with volume V (Boyle's Law). If P = 100 when V = 5, what is P when V = 4?125. k = PV = 500. P = 500/4 = 125.
  33. If both x and y double in a direct variation, what happens to y/x?It stays the same (k). y/x = k always in direct variation. If both double: (2y)/(2x) = y/x = k. Unchanged.
  34. The formula F = kq₁q₂/r² shows F varies inversely with:. F = (kq₁q₂)/r². For fixed charges, F varies inversely with r² (distance squared).