Date | May 2018 | Marks available | 6 | Reference code | 18M.2.hl.TZ1.2 |
Level | HL only | Paper | 2 | Time zone | TZ1 |
Command term | Find | Question number | 2 | Adapted from | N/A |
Question
The equation \({x^2} - 5x - 7 = 0\) has roots \(\alpha \) and \(\beta \). The equation \({x^2} + px + q = 0\) has roots \(\alpha + 1\) and \(\beta + 1\). Find the value of \(p\) and the value of \(q\).
Markscheme
METHOD 1
\(\alpha + \beta = 5,\,\,\alpha \beta = - 7\) (M1)(A1)
Note: Award M1A0 if only one equation obtained.
\(\left( {\alpha + 1} \right) + \left( {\beta + 1} \right) = 5 + 2 = 7\) A1
\(\left( {\alpha + 1} \right)\left( {\beta + 1} \right) = \alpha \beta + \left( {\alpha + \beta } \right) + 1\) (M1)
\( = - 7 + 5 + 1 = - 1\)
\(p = - 7,\,\,q = - 1\) A1A1
METHOD 2
\(\alpha = \frac{{5 + \sqrt {53} }}{2} = 6.1 \ldots {\text{;}}\,\,\beta = \frac{{5 - \sqrt {53} }}{2} = - 1.1 \ldots \) (M1)(A1)
\(\alpha + 1 = \frac{{7 + \sqrt {53} }}{2} = 7.1 \ldots {\text{;}}\,\,\beta + 1 = \frac{{7 - \sqrt {53} }}{2} = - 0.1 \ldots \) A1
\(\left( {x - 7.14 \ldots } \right)\left( {x + 0.14 \ldots } \right) = {x^2} - 7x - 1\) (M1)
\(p = - 7,\,\,q = - 1\) A1A1
Note: Exact answers only.
[6 marks]