JAMB Mathematics Past Questions & Answers - Page 162

806.

Rationalize the denominator of the expression \(\frac{6 + 2\sqrt{5}}{4 - 3\sqrt{6}}\)

A.

\(\frac{12+ 4\sqrt{5 + 7} 5 + 6\sqrt{3}}{39}\)

B.

\(\frac{-(24 + 18\sqrt{6} + 8\sqrt{5} + 6\sqrt{30})}{38}\)

C.

\(\frac{24 + 3\sqrt{6 + 8} 5 + 6\sqrt{30}}{19}\)

D.

\(\frac{-15 + 3\sqrt{5 + 18} 5 + 6\sqrt{30}}{36}\)

E.

\(\frac{-(12 + 4\sqrt{5} +9\sqrt{6} + 3\sqrt{30})}{19}\)

Correct answer is B

Rationalize using the reciprocal of the denominator to multiply through 

(i.e. Multiply both numerator and denominator using \(4 + 3\sqrt{6}\) )

Watch your signs in the course of this.

807.

A square of cardboard is taped at the perimeter by a piece of ribbon 20cm long. What is the area of the board?

A.

20sq.cm

B.

100sq.cm

C.

25sq.cm

D.

16sq.cm

E.

36sq.cm

Correct answer is C

Area of a square = 4(5) where S is each sides of the square

Perimeter = 20(given)

4S = 20

S = \(\frac{20}{4}\)

= 5

Area s2 = 52

= 25

808.

Multiply (3x + 5y + 4z) by (2x - 3y + z)

A.

6x2 + xy - 15y2 + 4z2 + 11xz - 7yz

B.

6x2 + 3xy - 15y2 + 4z2

C.

6x2 + 3xy - y2 + 4z2

D.

6x2 + 3xy - 15y + z2

Correct answer is A

(3x + 5y + 4z)(2x - 3y + z)

6x2 + 9xy + 3x2 + 10xy - 15y2 + 5yz + 8xz - 12yz + 4z2

= 6x2 + xy - 15y2 + 4z2 + 11xz - 7yz

809.

A trader goes to Ghana for y days with y cedis. For the first x days, he spends X cedis per day. The amount he has to spend per day for the rest of his stay is

A.

\(\frac{y(y - x)}{y - x}\) cedis

B.

\(\frac{Yy - Xx)}{y - x}\) cedis

C.

\(\frac{Y - Xy)}{y - x}\) cedis

D.

\(\frac{Y - X}{y - x}\) cedis

E.

\(\frac{Y - Xx}{y - x}\) cedis

Correct answer is E

The amount he has to spend per day for the rest of his stay is \(\frac{Y - Xx}{y - x}\) cedis

810.

The solution of the equation x2 - 2x = 8 is

A.

x = 0 or 2

B.

x = -2 or 4

C.

x = 2

D.

x = -4

E.

x = 2 or 4

Correct answer is B

x2 - 2x = 8 = 8

x2 - 2x - 8 = 0

(x2 - 4x) + (2x - 8) = 0

When x + 2 = 0

x = -2, when x - 4 = 0

x = 4

-2 or 4