Fractorise:
`81-49x ^(2)`

Answer

To factorize the expression \( 81 - 49x^2 \), we can follow these steps:

### Step 1: Identify the squares
We can rewrite \( 81 \) and \( 49x^2 \) as squares:
- \( 81 = 9^2 \)
- \( 49x^2 = (7x)^2 \)

### Step 2: Recognize the difference of squares
The expression \( 81 - 49x^2 \) can now be expressed as:
\[ 9^2 - (7x)^2 \]
This is in the form of \( a^2 - b^2 \), where \( a = 9 \) and \( b = 7x \).

### Step 3: Apply the difference of squares formula
We can use the difference of squares formula:
\[ a^2 - b^2 = (a + b)(a - b) \]
Substituting \( a \) and \( b \):
\[ (9 + 7x)(9 - 7x) \]

### Final Answer
Thus, the factorization of \( 81 - 49x^2 \) is:
\[ (9 + 7x)(9 - 7x) \]

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