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Example

Simplifying (2+3)(43)(2 + \sqrt{3})(4 - \sqrt{3})

Multiply two binomials that each contain a square root by applying the FOIL method, then simplify and combine the four resulting products.

(2+3)(43)(2 + \sqrt{3})(4 - \sqrt{3})

Apply FOIL to obtain four products:

  • First: 24=82 \cdot 4 = 8
  • Outer: 2(3)=232 \cdot (-\sqrt{3}) = -2\sqrt{3}
  • Inner: 34=43\sqrt{3} \cdot 4 = 4\sqrt{3}
  • Last: 3(3)=3\sqrt{3} \cdot (-\sqrt{3}) = -3

Write all four products:

823+4338 - 2\sqrt{3} + 4\sqrt{3} - 3

Combine the constant terms: 83=58 - 3 = 5. Combine the like radical terms: 23+43=23-2\sqrt{3} + 4\sqrt{3} = 2\sqrt{3}.

(2+3)(43)=5+23(2 + \sqrt{3})(4 - \sqrt{3}) = 5 + 2\sqrt{3}

When FOIL is applied to binomials containing square roots, the Last product often involves a square root multiplied by itself, which yields an integer (here 33=3\sqrt{3} \cdot \sqrt{3} = 3). The Outer and Inner products are typically like radicals that can be combined, just as they would be like terms in standard polynomial multiplication.

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Updated 2026-04-21

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