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Evaluation of Algebraic Expressions by Substituting a Value for the Variable.

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Finding the Value of an Expression:

The value of the expression depends on the value of the variable from which the expression is formed. There are a number of situations in which we need to find the value of an expression, such as when we wish to check whether a particular value of a variable satisfies a given equation or not.

1. Expressions with One Variable:

Find the value of the expression n3 + 5n2 + 5n - 2 when x = - 2.

Solution:
Now, for n = -2,

n3 + 5n2 + 5n - 2

= (-2)3 + 5(-2)2 + 5(-2) - 2

= - 8 + 20 – 10 - 2

= - 8 + 8

= 0.

2. Expressions with two or more variables:

Find the value of the expression a2 + 2ab + b2 when a = 3, b = 2.

Solution:

a2 + 2ab + b2, we get

a2 + 2ab + b2

= 32 + 2 × 3 × 2 + 22

= 9 + 2 × 6 + 4

= 9 + 12 + 4

= 25.

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