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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