Question

28x² – 7y² is equal to ______.

Options

• 7(x + 4y) (x – 4y)

• 7(4x + y) (4x – y)

• 7(2x + y) (2x – y)

• 7(x + y) (x – y)

Answer 1

28x² – 7y² is equal to 7(2x + y) (2x – y).

Explanation:

Let’s factorise the given expression:

28x² – 7y²

Step 1: Factor out the common factor of 7:

28x² – 7y² = 7(4x² – y²)

Step 2: Recognise that 4x² – y² is a difference of squares:

4x² – y² = (2x + y) (2x – y)

Step 3: Substitute back into the expression:

7(4x² – y²) = 7(2x + y) (2x – y)

Thus, the factorisation is 7(2x + y) (2x – y)