4MA0 Higher January 2018 Paper 3 Q17
17 Make \(a\) the subject of \(x = \sqrt{\dfrac{2b - a}{7 - am}}\)
(4)
| Scheme | Marks |
|---|---|
| \(x^2 = \dfrac{2b - a}{7 - am}\) | M1 |
| \(x^2(7 - am) = 2b - a\) | M1 |
| \(7x^2 - 2b = amx^2 - a\) or \(a - amx^2 = 2b - 7x^2\) | M1 |
| \(a = \dfrac{7x^2 - 2b}{mx^2 - 1}\) oe | A1 |
| (4) |
Notes
M1: for squaring both sides
M1: for multiplying by \(7 - am\) in a correct equation
allow \(x^2 \times 7 - am = 2b - a\)
\(7 - am \times x^2 = 2b - a\)
M1: for isolating terms in \(a\) in a correct equation
A1: or for \(a = \dfrac{2b - 7x^2}{1 - mx^2}\)
oe with \(a\) as the subject