10 questions · Form 4 Additional Mathematics Bab 6: Linear Law
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?
Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.
1. 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.
2. 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.
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 yx against x passes through (1, 3) and (3, 7). Find the equation connecting y and x.
Answer: A
Gradient m = 7 - 33 - 1 = 42 = 2. Y - 3 = 2(X - 1) => Y = 2X + 1. Since Y = yx and X = x: yx = 2x + 1 => y = 2x² + x.
5. 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.
6. 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.
7. If a graph of 1y against 1x is plotted for the equation y = xpx + q, what is the gradient m?
Answer: A
Invert both sides: 1y = px + qx = p + q(1x) => 1y = q(1x) + p. Plotted 1y against 1x, gradient m = q and intercept c = p.
8. Variables x and y are related by y = ax + b. A graph of xy against x gives a straight line with gradient 4 and y-intercept 6. Find the values of a and b.
Answer: A
Multiply y = ax + b by x: xy = bx + a. Thus Y = xy, X = x, gradient m = b = 4, and intercept c = a = 6.
9. 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.
10. Convert the non-linear equation y = ax² + bx into linear form Y = mX + c when plotting yx against x.
Answer: A
Dividing both sides of y = ax² + bx by x gives yx = ax + b. Comparing with Y = mX + c gives Y = yx, X = x, gradient m = a, and vertical intercept c = b.