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WAEC Further Mathematics Past Questions & Answers - Page 3

11.

The velocity of a body of mass 4.56 kg increases from (10ms1,060o)to(50ms1,060o) in 16 seconds . Calculate the magnitude of force acting on it.

A.

17.1 N

B.

11.4 N

C.

36.5 N

D.

5.7 N

Correct answer is B

m=4.56kg;t=16s;v1=(10ms1,060o);v2=(50ms1,060o)

Notice that there is no change in the direction of the velocity

So,we don't need to write it in a vector form

a=\frac{∆v}{t}=\frac{50 - 10}{16}

a=\frac{40}{16}=2.5ms^{-2}

F = ma = 4.56 x 2.5

∴ F = 11.4 N

12.

Given that \frac{3x + 4}{(x - 2)(x + 3)}≡\frac{P}{x + 3}+\frac{Q}{x - 2},find the value of Q

A.

2

B.

-2

C.

1

D.

-1

Correct answer is A

\frac{3x + 4}{(x - 2)(x + 3)}≡\frac{P}{x + 3}+\frac{Q}{x - 2}

\frac{3x + 4}{(x - 2)(x + 3)}=\frac{P(x-2)+Q(x+3)}{(x-2)(x+3)}

=3x+4=P(x-2)+Q(x+3)

=3x+4=Px-2P+Qx+3Q

=3x+4=Px+Qx-2P+3Q

=3x+4=(P+Q)x-2P+3Q

Equating x and the constants

P+Q=3------(i)

2P+3Q=4-------(ii)

From equation (i)

P=3-Q------(iii)

Substitute (3-Q) for P inequation (ii)

=-2(3-Q)+3Q=4

=-6+2Q+3Q=4

=-6+5Q=4

=5Q=4+6

=5Q=10

∴Q=\frac{10}{5}=2

13.

If 3x^2 + p x + 12 = 0 has equal roots, find the values of p .

A.

±12

B.

±3

C.

±4

D.

±6

Correct answer is A

The general form of a quadratic equation is:

x^2-(sum of roots) = 0

For equal roots it's:x^2 - 2(α)+(α)^2=0

3x^2+px+12=0

Divide through by 3

= x^2+\frac{p}{3}x+4=0

=x^2-(-\frac{p}{3})x+4=0

So,α^2=4

= α = √4 = ±2

Also,-\frac{p}{3}= 2α

When α = 2

-\frac{p}{3} = 2(2)=4

=p=-12

When α =-2

-\frac{p}{3}=2(-2)=-4

= p = 12

∴ values of p = ±12

14.

If α and β are the roots of 7x2 +12x - 4 = 0,find the value of \frac{αβ}{(α + β)^2}

A.

\frac{7}{36}

B.

- \frac{36}{7}

C.

\frac{36}{7}

D.

- \frac{7}{36}

Correct answer is D

The general form of a quadratic equation is:

x^2 -(sum of roots)x +(product of roots) = 0

7x^2+12x-4=0

Divide through by 7

=x^2+\frac{12}{7}x-\frac{4}{7}=0

=x^2-(-\frac{12}{7})x+(-\frac{4}{7})=0

\therefore sum of roots = -\frac{12}{7}, and products of roots =-\frac{4}{7}

α + β = -\frac{12}{7}, αβ = -\frac{4}{7}

\frac{αβ}{(α + β)^2} = \frac{\frac{-4}{7}}{(\frac{-12}{7})^2}

=\frac{\frac{-4}{7}}{\frac{144}{49}}=-\frac{4}{7}\times\frac{49}{144}

\therefore - \frac{7}{36}

15.

>Evaluate: \int(2x + 1)^3 dx

A.

8(2x + 1)^2 + k

B.

6(2x + 1)^2 + k

C.

\frac{1}{8} (2x + 1)^4 + k

D.

\frac{1}{6} (2x + 1)^4 + k

Correct answer is C

Using substitution method, Let u = 2x + 1

\frac{du}{dx}=2==>du=2dx==>dx=\frac{du}{2}

=\int\frac{u^3}{2} du = \frac{1}{2}\int u^3 du

=\frac{1}{2}(\frac{u^4}{4})=\frac{u^4}{8}

\therefore\frac{1}{8} (2x + 1)^4 + k