We know that, From formula, (a + b)(a – b) = a 2 – b 2 (2x + 5)(2x – 5) = (2x) 2 – (5) 2 = 4x 2 – 25

(2x + 5)(2x - 5) = ?

We know that,

From formula, (a + b)(a – b) = a² – b²

(2x + 5)(2x – 5) = (2x)² – (5)²

= 4x² – 25