Example

Multiplying (3xy)(2x5)(3x - y)(2x - 5) Using the FOIL Method

Multiply (3xy)(2x5)(3x - y)(2x - 5) using the FOIL method — both binomials involve subtraction and contain different variables (xx and yy), which means the Outer and Inner products may not be like terms.

Step 1 — First: Multiply the first terms: 3x2x=6x23x \cdot 2x = 6x^2.

Step 2 — Outer: Multiply the outermost terms: 3x(5)=15x3x \cdot (-5) = -15x.

Step 3 — Inner: Multiply the innermost terms: (y)2x=2xy(-y) \cdot 2x = -2xy.

Step 4 — Last: Multiply the last terms: (y)(5)=5y(-y) \cdot (-5) = 5y.

Writing all four products in order gives:

6x215x2xy+5y6x^2 - 15x - 2xy + 5y

Step 5 — Combine like terms: Check each term's variable structure: 6x26x^2 contains x2x^2, 15x-15x contains xx, 2xy-2xy contains both xx and yy, and 5y5y contains yy. No two terms share the same variable structure, so there are no like terms to combine.

The result is 6x215x2xy+5y6x^2 - 15x - 2xy + 5y. This example illustrates that when the two binomials involve different variables, the FOIL product does not simplify to a trinomial. The Outer product (15x-15x) and the Inner product (2xy-2xy) have different variable parts, so they cannot be combined, leaving the result with four terms.

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Updated 2026-04-21

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