Using an identity, find $47^2 - 53^2$ .

-36Correct answerYour answer-600Correct answerYour answer36Correct answerYour answer600Correct answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer B

Correct answer: B

$a^2 - b^2 = (a - b)(a + b)$ .
$(47 - 53)(47 + 53) = (-6)(100) = -600$ .

Worth noting

The first number is smaller, so the answer is negative; 600 has the sign wrong. $-36$ comes from squaring the difference, $(47 - 53)^2 = 36$ , and keeping a minus sign; that is a different expression.

Concept: Difference of squares for quick arithmetic
Typical timeTypical: 45 s
Your timeYours: —

The rule this testsPowers, roots and surds

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Using an identity, find 472−53247^2 - 53^2472−532.

Explanation

Using an identity, find $47^2 - 53^2$ .