O-LevelAdditional MathematicsStraight line graphs4037/12 · May/June 2022 · Q37 Marks
Variables x and y are such that, when lg(2y+1) is plotted against x², a straight line graph passing through the points (1, 1) and (2, 5) is obtained.
- (a)Find y in terms of x.[4]
- (b)Find the value of y when x = √3/2 .[1]
- (c)Find the value of x when y = 2.[2]
Mark scheme
Marking points from the official mark scheme (May/June 2022). The mark or mark type is shown in brackets.
- [B1] Gradient = 4 soi
- [B1] Intercept = -3 soi
- [M1] For lg(2y +1)= their m(x²)+ their c
- [A1] y = (10^(4x²-3) - 1)/2 or y = (10^(4x²)/1000 - 1)/2
- [B1] y = 0 (Must have at least 3 marks from part (a))
- [M1 Dep on M mark in part (a)] for use of y = 2 in their y = 1/2 (10^(4x²-3)-1)
- [A1] x = (±) 0.962 or better
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