JAMB Mathematics Past Questions & Answers - Page 297

1,481.

If y = 243(4x + 5)-2, find \(\frac{dy}{dx}\) when x = 1

A.

\(\frac{-8}{3}\)

B.

\(\frac{3}{8}\)

C.

\(\frac{9}{8}\)

D.

-\(\frac{8}{9}\)

Correct answer is A

y = 243(4x + 5)-2, find \(\frac{dy}{dx}\)

= -1944(4x + 5)-3

= 1944(9)-3

\(\frac{dy}{dx}\) when x = 1

= -\(\frac{1944}{9^3}\)

= -\(\frac{1944}{729}\)

= \(\frac{-8}{3}\)

1,482.

From the top of a vertical mast 150m high., two huts on the same ground level are observed. One due east and the other due west of the mast. Their angles of depression are 60° and 45° respectively. Find the distance between the huts

A.

150(1 + \(\sqrt{3}\))m

B.

50( \(\sqrt{3}\) - \(\sqrt{3}\))m

C.

150 \(\sqrt{3}\)m

D.

\(\frac{50}{\sqrt{3}}\)m

Correct answer is B

\(\frac{150}{Z}\) = tan 60o,

Z = \(\frac{150}{tan 60^o}\)

= \(\frac{150}{3}\)

= 50\(\sqrt{3}\)cm

\(\frac{150}{X x Z}\) = tan45o = 1

X + Z = 150

X = 150 - Z

= 150 - 50\(\sqrt{3}\)

= 50( \(\sqrt{3}\) - \(\sqrt{3}\))m

1,483.

solve the equation cos x + sin x \(\frac{1}{cos x - sinx}\) for values of such that 0 \(\leq\) x < 2\(\pi\)

A.

\(\frac{\pi}{2}\), \(\frac{3\pi}{2}\)

B.

\(\frac{\pi}{3}\), \(\frac{2\pi}{3}\)

C.

0, \(\frac{\pi}{3}\)

D.

0, \(\pi\)

Correct answer is D

cos x + sin x \(\frac{1}{cos x - sinx}\)

= (cosx + sinx)(cosx - sinx) = 1

= cos2x + sin2x = 1

cos2x - (1 - cos2x) = 1

= 2cos2x = 2

cos2x = 1

= cosx = \(\pm\)1 = x

= cos-1x (\(\pm\), 1)

= 0, \(\pi\) \(\frac{3}{2}\pi\), 2\(\pi\)

(possible solution)

1,484.

The midpoint of the segment of the line y = 4x + 3 which lies between the x-ax 1 is and the y-ax 1 is

A.

(\(\frac{3}{2}\), \(\frac{3}{2}\))

B.

(\(\frac{2}{3}\), \(\frac{3}{2}\))

C.

(\(\frac{3}{8}\), \(\frac{3}{2}\))

D.

(-\(\frac{3}{8}\), \(\frac{3}{2}\))

Correct answer is D

y = 4x + 3

when x = 0, y = 3 \(\to\) (0, 3)

when y = 0, x = -\(\frac{3}{4}\) \(\to\) (\(\frac{3}{4}\), 0)

mid-point \(\frac{0 + (-{\frac{3}{4}})}{2}\), \(\frac{3 + 0}{4}\)

-\(\frac{3}{8}\), \(\frac{3}{2}\)

1,485.

If the distance between the points (x, 3) and (-x, 2) is 5. Find x

A.

6.0

B.

2.5

C.

\(\sqrt{6}\)

D.

\(\sqrt{3}\)

Correct answer is C

d2 = (y - y)2 + (x - x)2

5 = 4x2 + 1 = 25= 4x2 + 1

= 4x2 = 25 - 1= 24

x2 = \(\frac{24}{4}\)

x = \(\sqrt{6}\)