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# Ex.12.3 Q3 Algebraic Expressions Solution - NCERT Maths Class 7

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## Question

Find the value of the following expressions, when $$x = \,–1$$

(i) $$2x - 7$$

(ii) $$- x + 2$$

(iii) $${x^2} + 2x + 1$$

(iv) $$2{x^2} - x - 2$$

Video Solution
Algebraic Expressions
Ex 12.3 | Question 3

## Text Solution

What is Known?

Value of $$x$$

What is unknown?

Value of the given expressions.

Reasoning:

This is based on concept of putting given value of variable and then performing the arithmetic operation as given in the question.

Steps:

Value of $$x$$ is given as $$–1$$

(i) $$2x - 7$$

\begin{align}& = 2 \times - 1 - (7)\\& = - 2 - 7\\{\rm{ Ans }} & = - 9\end{align}

(ii) $$- x + 2$$

\begin{align}& = - \left( { - 1} \right) + 2\\& = 1 + 2\\{\rm{Ans}} & = 3\end{align}

(iii) $${x^2} + 2x + 1$$

\begin{align}& = {\left( { - 1} \right)^2} + \left( {2 \times - 1} \right) + 1\\& = - 1 \times - 1 + \left( { - 2} \right) + 1\\& = 1 - 2 + 1\\{\rm{ Ans}} & = 0\end{align}

(iv) $$2{x^2} - x - 2$$

\begin{align}&= 2{{\left( { - 1} \right)}^2} - \left( { - 1} \right) - 2\\&= 2 \times - 1 \times - 1 + 1 - 2\\&= 2 + 1 - 2\\{\rm{ Ans }} &= 1\end{align}

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