1. Evaluating an expression with two variable

2. Substituting 2 in place of m, we get
Value of an expression
To find the value of an algebraic expression, we need to substitute the value of the variable in the algebraic expression
For example: Value of m + 8 for m = 2 will be
m+8
Substituting 2 in place of m, we get
(2) + 8 = 10

3. Substituting the value 3 for x and -2 for y, we get
Example 1: Find a value for the expression x + y when x = 3 and y = -2
x+y
Substituting the value 3 for x and -2 for y, we get
x+y =
(3) + (-2)
= 3 - 2
= 1
1 is the value of the expression
Take out x and replace it with 3.
Take out y and replace it with -2.
Ans: 1

4. Replace c with 2 and b with 5 = 3 x (2) + 2 x ( 5)
Example 2: Find a value for the expression 3c + 2b when c = 2 and b = 5
3 c b
= 3 x c x b
Replace c with 2 and b with 5
= 3 x (2) x ( 5) =
= 16
16 is the value of the expression
Ans: 16

5. Replace m with -2 and n with 7 = 4 x (-2) x (7) + 2
Example 3: Find a value for the expression 4mn + 2 when m = -2 and n = 7
4mn + 2
= 4 x m x n
Replace m with -2 and n with 7
= 4 x (-2) x (7) + 2
= x 7 + 5 = =
-51 is the value of the expression
Ans: 11

6. Try these Find the value for the expression.
a) 2a - 8b when a = 3 and b =4
b) -9xy + 4 when x = 2 and y = 5