(2b-3)(5b+7)+21=0
10b² + 14b - 15b - 21 + 21 = 0
10b² - b = 0
b(10b - 1) = 0
b = 0 10b - 1 = 0 ; 10b = 1 ; b =
ответ: b = 0 ; b =
(2b-3)(5b+7)+21=0
10b² + 14b - 15b - 21 + 21 = 0
10b² - b = 0
b(10b - 1) = 0
b = 0 10b - 1 = 0 ; 10b = 1 ; b =![\frac{1}{10}](/tpl/images/5177/6828/525ac.png)
ответ: b = 0 ; b =![\frac{1}{10}](/tpl/images/5177/6828/525ac.png)