Question

# Find the value of the following expression when n = 2. (i) 5n – 2(ii) $5{{n}^{2}}+5n-2$

Hint: We will substitute the values of ‘n’ in the given expression. We have two expressions one is linear and the second one is quadratic in the variable ‘n’. So, by substituting n = 2 in the given expression we will get the answer.

In the above question, we have been given to find the value of the following expression when n = 2.
(i) 5n – 2
This is a linear expression in the variable ‘n’. Now we will substitute n = 2 in the given linear expression, we will get,
$5n-2=5\times 2-2$
$\Rightarrow 5n-2=10-2$
$=8$
Hence, the value of the expression at n= 2 is equal to 8.
(ii) $5{{n}^{2}}+5n-2$
The above expression is in the form of $a{{x}^{2}}+bx+c$, so it is a quadratic expression. Now, we will substitute n = 2 in the given quadratic expression, we get,
$5{{n}^{2}}+5n-2=5\times {{\left( 2 \right)}^{2}}+5\times 2-2$
$\Rightarrow 5{{n}^{2}}+5n-2=20+10-2$
$=28$
Hence, the value of the expression at n = 2 equals to 28.
Therefore, the value of the expression (i) 5n – 2 and (ii) $5{{n}^{2}}+5n-2$ at n = 2 are 8 and 28 respectively.

Note: Students have to be careful while substituting the value of ‘n’ in the expression (ii). Also, students have to remember an expression is a sentence with a minimum of two numbers or variables, and at least one math operation.