А +36 = 4/3
1/3 а = 36
а= 108
4х² + Зх - 1 = 0
D = 3² - 4 × 4 × (-1) = 9 + 16 = 25
х (1) = -3 + корень с 25 ÷ 2 × 4 = 2 ÷ 8 = 0, 25
х (2) = -3 - корень с 25 ÷ 2 × 4 = -8 ÷ 8 = -1
1/5+8/25+7/25=5/25+8/25+7/25=20/25=4/5
7/15+2/5+5/6=14/30+12/30+25/30=51/30=17/10=1.7/10
39/40-19/28=273/280-190/280=83/280