Variable Expressions

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Variables are the alphabets written in an expression and they are denoted by letters or alphabets because they can take in any number as their value according to the given question. Therefore unlike constants which are fixed as they are numbers, variables vary in every question and we have the choice to assign them numbers as per the given question. Variable expressions are the expressions which contain variables along with the constants and these variables help us estimate the value of the given expression.

Example 1: What is the value of the given algebraic expression, 4x– 3+ 2x+ 9 if the value of x is 2?

Now we have to find the value of the above expression when x = 2 and in order to find the value, we should

plug-in ‘2’ in the place of ‘x’.

This implies: 4x– 3+ 2x+ 9= 4(2) – 3+ 2(2)+ 9.

This gives: 8– 3+ 4+ 9

Now calculate the values starting from the left side of the expression.

8– 3+4+9= 18.

Hence the value of the expression is 18.
 
Example 2: What is the value of the given algebraic expression, 5a + 6 + 10a if the value of ‘a’ is -1?

Now we have to find the value of the above expression when a = -1 and in order to find

the value, we should plug-in ‘-1’ in the place of ‘a’.

This implies: 5a+ 6+ 10a = 5(-1) + 6+ 10(-1).

This gives: -5 + 6 - 10

Now calculate the values starting from the left side of the expression.

1 – 10= -9

Hence the value of the expression is -9.

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