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

The rule done right

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

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$Math: Completing the Square$ Math: Completing the Square Infographic
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$Math: Factoring by Grouping$ Math: Factoring by Grouping Infographic
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algebra exponents