Test Index

BECE Mathematics 2021 Paper

© africaexams.com

Question : 40

Total: 40

Simplify

3 (5 a^2+2 c) -2 a(1-3 a)-6 c

$21 a^2-2 a-6 c$
$13 a^2-2 a-12 c$
$13 a^2-2 a$
$21 a^2-2 a$

Solution:

Expand the brackets first

Concept

\; a(b+c)=a \times b + a \times c

\; a(b-c)=a \times b - a \times c

\; 3 (5 a^2+2 c) =3 \times 5 a^2+3 \times 2 c

\; 3 (5 a^2+2 c) =15 a^2+6 c

\; -2 a(1-3 a) = -2 a \times 1 - 2 a \times -3 a

NOTE: -

x-=+

and

a \times a = a^2

\; -2 a(1-3 a) = -2 a + 6 a^2

\; 3 (5 a^2+2 c) -2 a(1-3 a)-6 c = 15 a^2+6 c-2 a+6 a^2-6 c

Group like terms

\; 3 (5 a^2+2 c) -2 a(1-3 a)-6 c = 15 a^2+6 a^2-2 a+6 c-6 c

\; 3 (5 a^2+2 c) -2 a(1-3 a)-6 c = 21 a^2-2 a+0

\; 3 (5 a^2+2 c) -2 a(1-3 a)-6 c = 21 a^2-2 a

© africaexams.com

Go to Question:

Prev Question