已知{a+b=3.5与a-b=1.5求4a方+3ab-b方的值 ————— 4a方b-ab方
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解: 解方程组a + b = 3.5a - b = 1.5得a = 2.5，b = 1那么4a^2 + 3ab - b^2 = (4a - b)(a + b) = (4×2.5 - 1)×3.5 = 33.254a^2b-ab^2 = ab(4a - b) = 2.5×1×(4×2.5 - 1) = 23.75
已知{a+b=3.5与a-b=1.5求4a方+3ab-b方的值 ————— 4a方b-ab方
解: 解方程组a + b = 3.5a - b = 1.5得a = 2.5，b = 1那么4a^2 + 3ab - b^2 = (4a - b)(a + b) = (4×2.5 - 1)×3.5 = 33.254a^2b-ab^2 = ab(4a - b) = 2.5×1×(4×2.5 - 1) = 23.75