Method 1:
Use distributive property: (a + b)(c + d) = ac + ad + bc + bd
(x + 5)(x + 5) = (x)(x) + (x)(5) + (5)(x) + (5)(5) = x² + 5x + 5x + 25
= x² + 10x + 25
Method 2:
a · a = a², therefore (x + 5)(x + 5) = (x + 5)².
Use (a + b)² = a² + 2ab + b².
(x + 5)² = x² + 2(x)(5) + 5² = x² + 10x + 25
