It is given that

[tex]\[
3\left(\begin{array}{cc}
p & -1 \\
0 & 4
\end{array}\right) - \left(\begin{array}{cc}
7 & q \\
-2 & 2r
\end{array}\right) = \frac{1}{2}\left(\begin{array}{cc}
16 & 8 \\
4 & -12
\end{array}\right)
\][/tex]

Find the value of:
(i) [tex]\(p\)[/tex] [2]
(ii) [tex]\(q\)[/tex] [2]
(iii) [tex]\(r\)[/tex] [2]



Answer :

To solve this problem, we need to find the values of [tex]\(p\)[/tex], [tex]\(q\)[/tex], and [tex]\(r\)[/tex] by equating the matrices on either side of the given equation. The steps below provide a detailed solution:

1. Calculate the right-hand side (RHS) of the equation:
[tex]\[ \text{RHS} = \frac{1}{2} \left( \begin{array}{cc} 16 & 8 \\ 4 & -12 \end{array} \right) \][/tex]
[tex]\[ \text{RHS} = \left( \begin{array}{cc} \frac{1}{2} \times 16 & \frac{1}{2} \times 8 \\ \frac{1}{2} \times 4 & \frac{1}{2} \times -12 \end{array} \right) \][/tex]
[tex]\[ \text{RHS} = \left( \begin{array}{cc} 8 & 4 \\ 2 & -6 \end{array} \right) \][/tex]

2. Calculate the left-hand side (LHS) of the equation:

- First, we calculate [tex]\(A\)[/tex]:
[tex]\[ A = 3 \left( \begin{array}{cc} p & -1 \\ 0 & 4 \end{array} \right) \][/tex]
[tex]\[ A = \left( \begin{array}{cc} 3p & -3 \\ 0 & 12 \end{array} \right) \][/tex]

- Then, we subtract matrix [tex]\(B\)[/tex]:
[tex]\[ B = \left( \begin{array}{cc} 7 & q \\ -2 & 2r \end{array} \right) \][/tex]

- Finally, we compute [tex]\(A - B\)[/tex]:
[tex]\[ A - B = \left( \begin{array}{cc} 3p & -3 \\ 0 & 12 \end{array} \right) - \left( \begin{array}{cc} 7 & q \\ -2 & 2r \end{array} \right) \][/tex]
[tex]\[ A - B = \left( \begin{array}{cc} 3p - 7 & -3 - q \\ 0 - (-2) & 12 - 2r \end{array} \right) \][/tex]
[tex]\[ A - B = \left( \begin{array}{cc} 3p - 7 & -3 - q \\ 2 & 12 - 2r \end{array} \right) \][/tex]

3. Equate the LHS and RHS matrices:
[tex]\[ \left( \begin{array}{cc} 3p - 7 & -3 - q \\ 2 & 12 - 2r \end{array} \right) = \left( \begin{array}{cc} 8 & 4 \\ 2 & -6 \end{array} \right) \][/tex]

By equating the corresponding elements, we obtain the following system of equations:
[tex]\[ 3p - 7 = 8 \quad \cdots \quad (1) \][/tex]
[tex]\[ -3 - q = 4 \quad \cdots \quad (2) \][/tex]
[tex]\[ 12 - 2r = -6 \quad \cdots \quad (3) \][/tex]

4. Solve the system of equations for [tex]\( p \)[/tex], [tex]\( q \)[/tex], and [tex]\( r \)[/tex]:

(i) For [tex]\( p \)[/tex]:
[tex]\[ 3p - 7 = 8 \][/tex]
[tex]\[ 3p = 15 \][/tex]
[tex]\[ p = 5 \][/tex]
[tex]\[ \boxed{5} \][/tex]

(ii) For [tex]\( q \)[/tex]:
[tex]\[ -3 - q = 4 \][/tex]
[tex]\[ -q = 7 \][/tex]
[tex]\[ q = -7 \][/tex]
[tex]\[ \boxed{-7} \][/tex]

(iii) For [tex]\( r \)[/tex]:
[tex]\[ 12 - 2r = -6 \][/tex]
[tex]\[ 12 + 6 = 2r \][/tex]
[tex]\[ 18 = 2r \][/tex]
[tex]\[ r = 9 \][/tex]
[tex]\[ \boxed{9} \][/tex]

Therefore, the values are:
(i) [tex]\( p = 5 \)[/tex]
(ii) [tex]\( q = -7 \)[/tex]
(iii) [tex]\( r = 9 \)[/tex]