JAMB Mathematics Past Questions & Answers - Page 167

831.

Solve the system of equation 2x + y = 32, 33y - x = 27

A.

(3, 2)

B.

(-3, 2)

C.

(3, -2)

D.

(-3, -2)

E.

(2, 2)

Correct answer is A

2x + y = 32, 33y - x = 27

2x + y = 25

33y + x = 33

x + y = 5

\(\frac{3y - x = 3}{4y = 8}\)

y = 2

832.

If it is given that 5x + 1 + 5x = 150, then the value of x is equal to

A.

3

B.

4

C.

1

D.

2

E.

\(\frac{1}{2}\)

Correct answer is D

5x + 1 + 5x = 150

5(5x) + 5x = 150

6(5x) = 150

5x = \(\frac{150}{6}\)

= 25

= 52

= 2

833.

Find the solution of the equation x + 2\(\sqrt{x} - 8\) = 0

A.

(4, 16)

B.

(2, 4)

C.

(4, 1)

D.

(1, 16)

E.

(16, 16)

Correct answer is A

x + 2\(\sqrt{x} - 8 = 0, Let \sqrt{x} = y\)

x = \(y^2\)

\(y^2 + 2y\) - 8 = 0

(y + 4)(x - 2) = 0

y = -4 or 2

x = 16 or 4

834.

What will be the value of k so that the quadratic equation kx2 - 4x + 1 = 0 has two equal roots?

A.

2

B.

3

C.

4

D.

8

E.

\(\frac{1}{4}\)

Correct answer is C

kx2 - 4x + 1 = 0, comparing with ax2 + bx + c = 0

a = k, b = -4, c = 1 for equal root b2 = 4ac

(-4)2 = 4k

k = \(\frac{16}{4}\)

= 4

835.

(\(\frac{x^a}{x^b}\))a + b = (\(\frac{x^{a + b}}{x^{a - b}}\))\(\frac{a^2}{b}\)

A.

x-a2

B.

xb2

C.

xa2 - b2

D.

\(\frac{1}{x^{a2 + b2}}\)

E.

xb2 - a2

Correct answer is D

(\(\frac{x^a}{x^b}\))a + b = (\(\frac{x^{a2 + ab}}{x^{b2 + ab}}\))

= xa2 - b2

{\(\frac{xa + b}{xa - b}\)} = xa + b - a + b

= x2b

= x2a

= xa2 - b2

= xb2 \(\div \) a2 = \(\frac{1}{x^\text a2 + b2}\)