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Answer:
(5x + 7y)² = 25x² + 70xy + 49y²
Step-by-step explanation:
(5x + 7y)² = 25x² + 70xy + 49y²
Because,
(5x + b)² = (5x)² + 2(5x)(b) + b²
2(5x)(b) = 70xy
b = 7y
b² = (7y)² = 49y²