Page 60 - Math Smart - 7

CHAPTER 3.2

In this chapter
eriving and Using

Pupils should be able to:

• substitute positive
integers into simple Formulae
linear expressions/
formulae
• derive and use simple
3.2.1 Substitution
formulae

Substituting into an algebraic expression means replacing the variables with the
given numbers to evaluate the expressions.

Example 1

\f X = 2, y = 3 and z = 5, find the values of the expressions.

a) 3x + b) 5 + 3y c) xz — yz
z
Solution
z
a) 3x + b) 5 + 3y xz — yz
= (3x2) +5 = 5 + (3 X 3) = (2x5) -(3x5)
5
= 6 + = 5 + = 10-15
9
= 11 = 14 = -5
Check My
Understanding

O x = l and y = 5, find the value of

a) ;*: + 5 b) x — y c) 3x d) 2x + 3y
e) Ay-2x f) x(3 + y) h) Ji -y
g) £
7
If
@ a = 2 and b = S, find the value of each expression.
a) a + b b) 3b c) a — b d) b — 3a
e) ^ f) 1 - f q) 3fl + 2/7 h) ^ - 3fo
b 2 ^ ^
@ p = 2, q = 4 and r = 1, find the value of each expression.
\f
a) p + q — r b) 3p + 2q + 5r c) 2p + q - 4r d) 2(p + q-5)
e) p(r + q) i) H g) Q - h) M
2 ^ 4 ^ 3
O When a = 3, b = 4 and c = 5, what is the value of each expression?

a) 2(abc) b) 0 c{ab) d) a^b
2

Introduction to Algebra and Equations