The variables x and y satisfy the equation xⁿy² = C, where n and C are constants. The graph of ln y against ln x is a straight line passing through the points (0.31, 1.21) and (1.06, 0.91), as shown in the diagram. [Figure 3.1]
- (a)Find the value of n and find the value of C correct to 2 decimal places.[5]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (Feb/Mar 2022). The mark or mark type is shown in brackets.
- [1] State or imply n ln x + 2 ln y = ln C
- [1] Substitute values of ln y and ln x, or equate gradient of line to ±½n, but not ± n, and solve for n
- [1] Obtain n = 0.8[0] or 0.8[00] or 4/5
- [1] Solve for C
- [1] Obtain C = 14.41
- [1] Obtain two correct equations in n and C by substituting x and y values in the given equation
- [1] Solve for n
- [1] Obtain n = 0.8[0] or 0.8[00] or 4/5
- [1] Solve for C
- [1] Obtain C = 14.41
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