Example

Multiplying (x+5)(x+9)(x + 5)(x + 9) Using the FOIL Method

Multiply (x+5)(x+9)(x + 5)(x + 9) using the FOIL method — both binomials involve only addition, so all four products will be positive.

Step 1 — First: Multiply the first terms of each binomial: xx=x2x \cdot x = x^2.

Step 2 — Outer: Multiply the outermost terms: x9=9xx \cdot 9 = 9x.

Step 3 — Inner: Multiply the innermost terms: 5x=5x5 \cdot x = 5x.

Step 4 — Last: Multiply the last terms of each binomial: 59=455 \cdot 9 = 45.

Writing all four products in order gives:

x2+9x+5x+45x^2 + 9x + 5x + 45

Step 5 — Combine like terms: The Outer and Inner products 9x9x and 5x5x are like terms: 9+5=149 + 5 = 14:

x2+14x+45x^2 + 14x + 45

The result is x2+14x+45x^2 + 14x + 45. This example demonstrates the basic FOIL pattern when both binomials contain only addition — all four individual products are positive, and the two middle terms combine into a single term, producing a trinomial.

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Updated 2026-04-21

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