10 questions · Form 4 Additional Mathematics Bab 6: Linear Law
If y - x = p x² + q, what variables should be plotted on the vertical and horizontal axes to obtain a straight line with gradient p?
Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.
1. If y - x = p x² + q, what variables should be plotted on the vertical and horizontal axes to obtain a straight line with gradient p?
Answer: A
Comparing y - x = p x² + q with Y = mX + c gives Y = y - x, X = x², gradient m = p, and intercept c = q.
2. Given the equation y = a √x + b/√x, which transformation yields a straight line with Y-intercept b when plotted against x?
Answer: A
Multiply y = a√x + b/√x by √x: y√x = ax + b. Plotted Y = y√x against X = x, gradient m = a and vertical intercept c = b.
3. Which of the following describes a key requirement when drawing a line of best fit?
Answer: A
A line of best fit does not need to pass through all points or the origin; points off the line should be evenly and symmetrically distributed above and below it.
4. A straight line graph of xy against x² has a gradient of 3 and a Y-intercept of -4. Express y in terms of x.
Answer: A
The linear equation is xy = 3x² - 4. Divide both sides by x: y = 3x - 4x.
5. When lg y is plotted against x for the equation y = 5(2^x), what is the vertical intercept c?
Answer: A
lg y = (lg 2)x + lg 5. Comparing with Y = mX + c gives gradient m = lg 2 and vertical intercept c = lg 5.
6. A plot of lg y against lg x gives a line with gradient m = 0.5 and Y-intercept c = 0.3010. Express y in terms of x.
Answer: A
lg y = 0.5 lg x + 0.3010 => lg y = lg(x0.5) + lg(100.3010) = lg(x0.5) + lg 2 = lg(2√x) => y = 2√x.
7. Experimental data for x and y gives a straight line when 1y is plotted against x². If the line passes through (0, 2) and (4, 14), find 1y when x = 3.
Answer: A
Gradient m = 14 - 24 - 0 = 124 = 3. Equation: 1y = 3x² + 2. When x = 3: 1y = 3(3²) + 2 = 3(9) + 2 = 29... Wait: 3(3) + 2 = 11 if X = x², at x = 3 => X = 9 => 3(9)+2 = 29. Re-evaluating: if points are (X=0, Y=2) and (X=4, Y=14) where X = x², then for x = 3, X = 9 => Y = 3(9) + 2 = 29. If points were (x²=0, 2) and (x²=4, 14), gradient = 3, so Y = 3X + 2. For X = 3 (i.e., x²=3), Y = 11.
8. Variables x and y are connected by p^x y = q. Express this in linear form Y = mX + c.
Answer: A
Take lg on both sides: lg(p^x y) = lg q => x lg p + lg y = lg q => lg y = (-lg p)x + lg q.
9. The non-linear relationship between x and y is given by y = a x^b. If lg y is plotted against lg x, what does the gradient m represent?
Answer: A
lg y = b lg x + lg a. Comparing with Y = mX + c where Y = lg y and X = lg x gives gradient m = b and intercept c = lg a.
10. The non-linear equation y = a b^x is expressed in linear form. What are the variables plotted on the vertical and horizontal axes?
Answer: A
Taking lg on both sides: lg y = lg(a b^x) = lg a + x lg b => lg y = (lg b)x + lg a. Thus Y = lg y and X = x.