Question

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

Answer 1

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.

Complete step-by-step 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.