The variables x and y satisfy the equation x = A(3⁻ʸ), where A is a constant.
- (a)Explain why the graph of y against lnx is a straight line and state the exact value of the gradient of the line.[3]
- (b)Calculate the value of A, giving your answer correct to 2 decimal places.[2]
Mark scheme
Marking points from the official mark scheme (May/June 2021). The mark or mark type is shown in brackets.
- [B1] State or imply ln x = ln A − y ln 3
- [B1] State that the graph of y against ln x has an equation that is linear in y and ln x, or has an equation of the standard form 'y = mx + c' and is thus a straight line
- [B1] State that the gradient is −1/ln 3
- [M1] Substitute ln x = 0, y = 1.3 and use correct method to solve for A
- [A1] Obtain answer A = 4.17 only
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