2014 - JAMB Mathematics Past Questions and Answers - page 2

2y² - 15xy + 18x²

2y² - 12xy - 3xy + 18x²

2y(y - 6x) - 3x(y - 6x)

(2y - 3x) (y - 6x)

if y - 1 is a factor of y³ + 4y² + ky - 6, then

f(1) = (1)³ + 4(1)2 + k(1) - 6 = 0 (factor theorem)

1 + 4 + k - 6 = 0

5 - 6 + k = 0

-1 + k = 0

k = 1

(y \propto w^2)

y = kw²

8 = k(2)²

8 = k(4)

k = 8/4

k = 2

Thus y = 2w²

When w = 3, y = 2(3)²

y = 2 x 9 = 18

(P \propto \frac{Q}{R})

(P = K \frac{Q}{R})

When Q = 36, R = 16, P = 27

Then substitute into the equation

(27 = K \frac{36}{16})

(K = \frac{27 \times 16}{36})

(K = 12)

So the equation connecting P, Q and R is

(P = \frac{12Q}{R})

Consider the range -3 < x < -1

= { -2, -1, 0}, for instance

When x = -2,

(\frac{-2 - 5}{-2 + 3} < -1)

(\frac{-7}{1} < -1)

When x = -1,

(\frac{-1 - 5}{-1 + 3} < -1)

(\frac{-6}{2} < -1)

= -3 < -1

When x = 0,

(\frac{0 - 5}{0 + 3} < -1)

(\frac{- 5}{3} < -1)

Hence -3 < x < 1

(\frac{x}{2} + \frac{3}{4} \leq \frac{5x}{6} - \frac{7}{12})

(12\frac{x}{2} + 12\frac{3}{4} \leq 12\frac{5x}{6} - 12\frac{7}{12})

6x + 9 (\leq) 10x - 7

6x - 10x (\leq) - 7 - 9

-4x (\leq) -16

-4x/-4 (\geq) -16/-4

x (\geq) 4

a + 3d = 13 .......... (1)

a + 9d = 31 .......... (2)

(2) - (1): 6d = 18

d = 18/6 = 3

From (1), a + 3(3) = 13

a + 9 = 13

a = 13 - 9 = 4

Hence,

T₂₄ = a + 23d

T₂₄ = 4 + 23(3)

T₂₄ = 4 + 69

T₂₄ = 73

Common ratio r of the G.P is

(r = \frac{T_n + 1}{T_n} = \frac{T_2}{T_1})

(r = \frac{\sqrt{10} + 2\sqrt{5}}{\sqrt{10} + \sqrt{5}})

(r = \frac{\sqrt{10} + 2\sqrt{5}}{\sqrt{10} + \sqrt{5}} \times \frac{\sqrt{10} - \sqrt{5}}{\sqrt{10} - \sqrt{5}} )

( = \frac{(\sqrt{10})(\sqrt{10}) + (\sqrt{10})(-\sqrt{5}) + (2\sqrt{5})(\sqrt{10}) + (2\sqrt{5})(-\sqrt{5})}{(\sqrt{10})^2 - (\sqrt{5})^2})

(\frac{10 - \sqrt{50} + 2\sqrt{50} - 10}{10 - 5})

(\frac{\sqrt{50}}{5})

(\frac{\sqrt{25 \times 2}}{5})

(\frac{5\sqrt{2}}{5})

(\sqrt{2})

x * y = x^y

x * 2 = 12 - x

Thus by comparison,

x = x, y = 2

But x * y = x * 2

x^y = 12 - x

x² = 12 - x

x² + x - 12 = 0

x² + 4x - 3x - 12 = 0

x(x + 4) - 3(x + 4) = 0

(x - 3)(x + 4) = 0

x - 3 = 0 or x + 4 = 0

So x = 3 or x = -4

(\begin{pmatrix}

5 & -6 \

2 & -7

\end{pmatrix}\begin{pmatrix}

5 \

2

\end{pmatrix} = \begin{pmatrix}

7 \

-11

\end{pmatrix})

By matrices multiplication;

5x - 6y = 7 ........(1)

2x - 7y = -11 ......(2)

2 x (1): 10x - 12y = 14 .......(3)

5 x (2): 10x - 35y = -55 ......(4)

(3) - (4): 23y = 69

y = 69/23 = 3