# Ex.12.3 Q2 Algebraic Expressions Solution - NCERT Maths Class 7

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## Question

If $$p = \,– 2$$, find the value of:

(i) $$4p + 7$$

(ii) $$- 3{p^2} + 4p + 7$$

(iii) $$- 2{p^3} - 3{p^2} + 4p + 7$$

Video Solution
Algebraic Expressions
Ex 12.3 | Question 2

## Text Solution

What is known?

Value of $$p$$.

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 $$p$$ is given as $$- 2$$

(i) $$4p + 7$$

\begin{align} &=\! 4 \!\times\!\! -\! 2 \!+\! \left( 7 \right)\\ &= \!-\! 8 \!+\! 7\\&{\rm{ Ans }} = \!-\! 1\end{align}

(ii) $$- 3{p^2} + 4p + 7$$

\begin{align}&= \!-\! 3 \!\times\! {{\left( { - 2} \right)}^2} \!+\!4 \!\times\! \left( { - 2} \right) \!+\! 7\\ &= \! \left( { - 3 \!\times\! \!- 2 \!\times\! \!- 2} \right) \!+\! \left( { - 8} \right) \!+\! 7\\ &= \!-\! 12 \!-\! 8 \!+\! 7\\&{\rm{ Ans }} = \!-\! 13\end{align}

(iii) $$- 2{p^3} - 3{p^2} + 4p + 7$$

\begin{align} &=\!-\!2{{\left( -2 \right)}^{3}}\!-\!3{{\left( -2 \right)}^{2}}\!+\!4\left( -2 \right)\!+\!7 \\ &=\!-\!2 \!\times\! \!-2\!\times\! \!-2\!\times\!\! -2\left( 3\!\times\! \!-2\!\times\! \!-2 \right)\!+\!\left( 4\!\times\! \!-2 \right)\!+\!7 \\ &=\!16\left( 12 \right)\!+\!\left( -8 \right)\!+\!7 \\ &\text{Ans} =\!3 \end{align}

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