Reformat the expression for clarity:

[tex]\[
\left(\begin{array}{ll}
2k & 1
\end{array}\right)
\left(k \quad 4\right) - 3k(k - 7)
\][/tex]



Answer :

Certainly! Let’s break down and solve the given expression step by step:

The expression to simplify is:

[tex]\[ \left(\begin{array}{ll}2k & 1\end{array}\right) \left(\begin{array}{ll} k \\ 4 \end{array}\right) - 3k(k-7) \][/tex]

### 1. Matrix Multiplication:
First, we need to multiply the two matrices:

[tex]\[ \left(\begin{array}{ll}2k & 1\end{array}\right) \left(\begin{array}{ll} k \\ 4 \end{array}\right) \][/tex]

The result of this multiplication is obtained by performing the dot product of corresponding elements:

[tex]\[ (2k \cdot k) + (1 \cdot 4) = 2k^2 + 4 \][/tex]

So,

[tex]\[ \left(\begin{array}{ll}2k & 1\end{array}\right) \left(\begin{array}{ll} k \\ 4 \end{array}\right) = 2k^2 + 4 \][/tex]

### 2. Simplifying the Subtraction Expression:
Next, we subtract the term [tex]\(3k(k - 7)\)[/tex]:

[tex]\[ 3k(k - 7) = 3k^2 - 21k \][/tex]

### 3. Combine Both Parts:
Now, we combine the results of our operations:

[tex]\[ 2k^2 + 4 - (3k^2 - 21k) \][/tex]

### 4. Distribute the Negative Sign:
Distribute the subtraction across the terms inside the parentheses:

[tex]\[ 2k^2 + 4 - 3k^2 + 21k \][/tex]

### 5. Combine Like Terms:
Now, combine the [tex]\(k^2\)[/tex] terms and the constant terms:

[tex]\[ (2k^2 - 3k^2) + 21k + 4 = -k^2 + 21k + 4 \][/tex]

So, the simplified result of the expression is:

[tex]\[ \boxed{-k^2 + 21k + 4} \][/tex]

This is the final answer.