Fractorise:
`14m -21`

Options

A. `5 (2m -3)`
B. `4 (2m -3)`
C. `7 (2m -3)`
D. `9 (2m -3)`

Answer

To factorise the expression \( 14m - 21 \), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the common factors**:
We need to look for the greatest common factor (GCF) of the coefficients of the terms in the expression. The coefficients are 14 and 21.

2. **Calculate the GCF**:
The GCF of 14 and 21 is 7.

3. **Rewrite the expression using the GCF**:
We can express each term in the expression \( 14m - 21 \) in terms of the GCF:
- \( 14m \) can be rewritten as \( 7 \times 2m \)
- \( 21 \) can be rewritten as \( 7 \times 3 \)

4. **Factor out the GCF**:
Now we can factor out 7 from the expression:
\[ 14m - 21 = 7 \times 2m - 7 \times 3 \]
This can be simplified to:
\[ 7(2m - 3) \]

5. **Final expression**:
Therefore, the factorised form of \( 14m - 21 \) is:
\[ 7(2m - 3) \]

### Final Answer:
\[ 14m - 21 = 7(2m - 3) \]