Question

(3a-4)-3(2a-5)a=0,2 найти a

Answer 1

$(3a-4)-3(2a-5)a=0.2\\3a-4-6a^{2} +15a=0.2\\18a-4-6a^{2} =0.2\\90a-20-30a^{2} = 1\\90a-21-30a^{2} =0\\10a^{2} -30a+7=0$

$D = 620$

$a_{1} = \frac{30+\sqrt{620} }{20} = \frac{15+\sqrt{155} }{10}$

$a_{2} = \frac{30-\sqrt{620} }{20} = \frac{15-\sqrt{155} }{10}$