Math

Treating (a + b) Squared as a Squared Plus b Squared

Squaring each term of a sum separately instead of expanding the whole product.

Quick check

Why students make it

Exponents distribute over multiplication, like (ab)2=a2b2(ab)^2 = a^2 b^2, so it feels like they should distribute over addition too. They do not.

The rule done right

Expand the square as a product: (a+b)2=(a+b)(a+b)=a2+2ab+b2(a+b)^2 = (a+b)(a+b) = a^2 + 2ab + b^2. The middle term 2ab2ab is the part that gets dropped.

Related resources

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