WAEC Mathematics Past Questions & Answers - Page 217

1,081.

The graph of the curve \(y = 2x^2 - 5x - 1\) and a straight line PQ were drawn to solve the equation \(2x^2 - 5x + 2 = 0\)
What is the equation of the straight line PQ?

A.

y = -1

B.

y = 1

C.

y = 3

D.

y = -3

Correct answer is D

Let the straight line PQ = y

2x\(^2\) - 5x - 1 - y = 2x\(^2\) - 5x + 2

y = 2x\(^2\) - 5x - 1 - 2x\(^2\) + 5x - 2 

y = -3

1,082.

which of the following is not quadratic expression?

A.

\(y = 2x^2 - 5x\)

B.

\(y=x(x-5)\)

C.

\(y = x^2 - 5\)

D.

y = 5(x-1)

Correct answer is D

A quadratic equation is an equation of the second order. The highest power in the equation is 2.

1,083.

If \(2x^2 + kx - 14 = (x+2)(2x-7)\), find the value of K

A.

-3

B.

5

C.

9

D.

11

Correct answer is A

\(2x^2 + kx - 14 = (x+2)(2x-7)\\
∴2x^2 + kx - 14 = 2x^2 - 3x - 14\)
equating coefficient K = -3

1,084.

if \(\frac{4m+3n}{4m-3n}=\frac{5}{2}\), find the ratio m:n

A.

7:4

B.

4:3

C.

3:4

D.

4:7

Correct answer is A

\(\frac{4m + 3n}{4m - 3n} = \frac{5}{2}\)

\(5(4m - 3n) = 2(4m + 3n)\)

\(20m - 15n = 8m + 6n\)

\(20m - 8m = 6n + 15n\)

\(12m = 21n\)

\(\frac{21}{12} = \frac{m}{n}\)

\(m : n = 7 : 4\)

1,085.

If \(\frac{y-3}{2}<\frac{2y-1}{3}\), which of the following is true?

A.

y > 7

B.

y < -7

C.

y > -7

D.

y < 7

Correct answer is C

\(\frac{y - 3}{2} < \frac{2y - 1}{3}\)

\(3(y - 3) < 2(2y - 1)\)

\(3y - 9 < 4y - 2\)

\(3y - 4y < -2 + 9\)

\(-y < 7\)

\(y > -7\)