先化简再求值 [(2a+b)平方+(2a+b).(b-2a)-6b]除2b 其中a=-1/2 b=3

[(2a+b)² + (2a+b)(b-2a) - 6b] / 2b 其中a = - 1/2 b = 3
= [(2a+b)² - (2a+b)(2a - b) - 6b] / 2b → (b-2a) ＝ - (2a - b)
= [(2a+b)(2a + b - 2a + b) - 6b] / 2b → 提取 (2a+b)
= [(2a+b)(2b) - 6b] / 2b
= [2a + b - 3]
= - 1 + 3 - 3
= - 1
[(2a+b)² + (2a+b)(b-2a) - 6b] / 2b 其中a = - 1/2 b = 3
= [(2a+b)² - (2a+b)(2a - b) - 6b] / 2b → (b-2a) ＝ - (2a - b)
= [(2a+b)² - ((2a)² - b²) - 6b] / 2b → (2a+b)(2a - b) = (2a)² - b²
= [(2a+b)² - (2a)² + b² - 6b] / 2b
= [4ab + b² + b² - 6b] / 2b → (2a+b)² - (2a)² = 4ab + b²
= [4ab + 2b² - 6b] / 2b
= [2a + b - 3]
= - 1 + 3 - 3
= - 1