CAIE
FP1
2015
June
Q8
10 marks
Standard +0.3
8 A line, passing through the point \(A ( 3,0,2 )\), has vector equation \(\mathbf { r } = 3 \mathbf { i } + 2 \mathbf { k } + \lambda ( 2 \mathbf { i } + \mathbf { j } - 2 \mathbf { k } )\). It meets the plane \(\Pi\), which has equation \(\mathbf { r } \cdot ( \mathbf { i } + 2 \mathbf { j } + \mathbf { k } ) = 3\), at the point \(P\). Find the coordinates of \(P\).
Write down a vector \(\mathbf { n }\) which is perpendicular to \(\Pi\), and calculate the vector \(\mathbf { w }\), where
$$\mathbf { w } = \mathbf { n } \times ( 2 \mathbf { i } + \mathbf { j } - 2 \mathbf { k } )$$
The point \(Q\) lies in \(\Pi\) and is the foot of the perpendicular from \(A\) to \(\Pi\). Use the vector \(\mathbf { w }\) to determine an equation of the line \(P Q\) in the form \(\mathbf { r } = \mathbf { u } + \mu \mathbf { v }\).
CAIE
FP1
2007
November
Q3
6 marks
Challenging +1.2
3 Prove by induction that, for all \(n \geqslant 1\),
$$\frac { \mathrm { d } ^ { n } } { \mathrm {~d} x ^ { n } } \left( \mathrm { e } ^ { x ^ { 2 } } \right) = \mathrm { P } _ { n } ( x ) \mathrm { e } ^ { x ^ { 2 } } ,$$
where \(\mathrm { P } _ { n } ( x )\) is a polynomial in \(x\) of degree \(n\) with the coefficient of \(x ^ { n }\) equal to \(2 ^ { n }\).
CAIE
FP1
2007
November
Q4
7 marks
Standard +0.8
4 The roots of the equation
$$x ^ { 3 } - 8 x ^ { 2 } + 5 = 0$$
are \(\alpha , \beta , \gamma\). Show that
$$\alpha ^ { 2 } = \frac { 5 } { \beta + \gamma } .$$
It is given that the roots are all real. Without reference to a graph, show that one of the roots is negative and the other two roots are positive.