JAMB Mathematics Past Questions & Answers - Page 256

1,276.

Which of the following is a factor of rs + tr - pt - ps?

A.

(p - s)

B.

(s - p)

C.

(r - p)

D.

(r + p)

Correct answer is C

rs + tr - pt - ps = rs - ps - tr - pt = (r - p)s + (r - p)t = (r - p)(s + t), hence r - p is a factor

1,277.

Factorize 1 - (a - b)2

A.

(1 - a - b)(1 - a + b)

B.

(1 + a - b)(1 - a + b)

C.

(1 - a + b)(1 - a + b)

D.

(1 + a + b)(1 + a + b)

Correct answer is B

1 - (a - b)2 = [1 + (a - b)][1 - a + b]

= (1 + a - b)(1 - a + b)

1,278.

Factorize m3 - 2m2 - m + 2

A.

(m2 + 1)(m - 2)

B.

(m - 1)(m + 1)(m + 2)

C.

(m - 2)(m + 1)(m - 1)

D.

(m2 + 2)(m - 1)

Correct answer is C

m3 - 2m2 - m + 2

Let f(m) = m3 - 2m2 - m2 + 2

= f(1)

= 1 - 2 - 2 + 2 = 0

∴ m - 1 is factor \(\frac{m^3 - 2m^2 - m^2 + 2}{m - 1}\)

= m2 - m - 2

= (m - 1)m2 - m - 2

= (m - 1)(m + 1)(m - 2)

1,279.

If g(x) = x2 + 3x + 4, find g(x + 1) - g(x)

A.

(x + 2)

B.

2(x + 2)

C.

(2x + 1)

D.

(x2 + 4)

Correct answer is B

g(x) = x2 + 3x + 4

= g(x + 1) = (x + 1)^2 + 3(x + 1) + 4

= x2 + 1 + 2x + 3x + 3 + 4

= x2 + 5x + 8

g(x + 1) - g(x) = x2 + 5x + 8 - (x2 + 3x + 4)

= x2 + 5x + 8 - x2 + 3x + 4

= 2x + 4

= 2(x + 2)

1,280.

If w varies inversely as \(\frac{uv}{u + v}\) and is equal to 8 when

u = 2 and v = 6, find a relationship between u, v, w.

A.

uvw = 16(u + v)

B.

16ur = 3w(u + v)

C.

uvw = 12(u + v)

D.

12uvw = u + v

Correct answer is C

W \(\alpha\) \(\frac{\frac{1}{uv}}{u + v}\)

∴ w = \(\frac{\frac{k}{uv}}{u + v}\)

= \(\frac{k(u + v)}{uv}\)

w = \(\frac{k(u + v)}{uv}\)

w = 8, u = 2 and v = 6

8 = \(\frac{k(2 + 6)}{2(6)}\)

= \(\frac{k(8)}{12}\)

k = 12

i.e 12 ( u + v) = uwv