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  • Please Solve R.D.Sharma class 12 Chapter 23 Scaler or Dot Products Exercise 23.1 Question 31 Sub Question 1 Maths Textbook Solution.

Please Solve R.D.Sharma class 12 Chapter 23 Scaler or Dot Products  Exercise 23.1 Question 31 Sub Question 1 Maths Textbook Solution.

Answers (1)

Answer:  \mid \vec{a}\mid =4 ,\mid \vec{b}\mid =2

Hint:  You must know the rules of solving vectors.

Given:   Find \mid \vec{a}\mid and \mid \vec{b}\mid b if \left ( \vec{a}+\vec{b} \right ).\left ( \vec{a}-\vec{b} \right )=12 and     

Solution: Given,

\begin{aligned} &|\vec{a}|=2|\vec{b}| \text { and }(\vec{a}+\vec{b}) \cdot(\vec{a}-\vec{b})=12 \\\\ &|\vec{a}|^{2}-|\vec{b}|^{2}=12 \\ \end{aligned}

\begin{aligned} (2|\vec{b}|)^{2}-|\vec{b}|^{2}=12 \\ \end{aligned}

\qquad 3|\vec{b}|^{2}=12 \\

|\vec{b}|^{2}=4 \\

|\vec{b}|=2 \\

|\vec{a}|=2|\vec{b}| \Rightarrow 2(2)=4 \\

\therefore|\vec{a}|=4 \text { and }|\vec{b}|=2

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