Answer:
40x² + 240x + 200
Explanation:
The area (A) of the rectangular pitch is calculated as
A = lb ( l is the length and b the breadth )
= (10x + 10)(4x + 20)
Each term in the second factor is multiplied by each term in the first factor, that is
10x(4x + 20) + 10(4x + 20) ← distribute both parenthesis
= 40x² + 200x + 40x + 200 ← collect like terms, thus
A = 40x² + 240x + 200 ← in standard form