Formulas & tables/Mathematics/Special products/Square of a sum

Square of a sum

(a+b)2=a2+2ab+b2(a+b)^2=a^2+2ab+b^2

Result unit: — (expression)

What it describes

The square of the sum of two expressions.

Symbols

a,ba, b
arbitrary expressions (numbers)

Where it comes from

The square of a sum is not just a2+b2a^2+b^2 — there is also the double product 2ab2ab. A common mistake is to leave it out.

When to use it

Expanding squares, simplifying, completing the square.

Example

Expand (x+3)2(x+3)^2.
Substitutiona=xa=x, b=3b=3.
Resultx2+6x+9x^2+6x+9.

Related formulas

Square of a difference Difference of squares

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