4 in bracket 2 x minus y whole square minus 9 (5 x + 3 y whole square
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Answer:
-209x² - 77y² - 286xy
Step-by-step explanation:
4 (2x - y)² - 9(5x + 3y)²
(a + b)² = a² + 2ab + b² and (a - b)² = a² - 2ab + b²
= 4 (4x² + y² - 4xy) - 9(25x² + 9y² + 30xy)
= 16x² + 4y² - 16xy - 225x² - 81y² - 270xy
= -209x² - 77y² - 286xy
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