16Hit1600
Advanced MathVery hardRecognising a perfect square of a known sum

Advanced Math practice question

If 2x + y = 10, what is the value of 4x² + 4xy + y²?

Answer: 100

4x² + 4xy + y² = (2x + y)². Since 2x + y = 10, the expression equals 10² = 100.

Common wrong answers

If you answered 10
10 is 2x + y itself; the expression is its SQUARE.
If you answered 20
20 is 2(2x + y), doubling instead of squaring.
If you answered 40
40 is 4 × 10, as if the expression were 4(2x + y).

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