3/4 = 0.75
2/5 = 0.4
0.75 - 0.4 = 0.35 - ответ
1) 2x² + 7x - 9 = 0
D = 7² - 4 * 2 * (- 9) = 49 + 72 = 121 = 11²
2) 100x² - 16 = 0
(10x - 4)(10x + 4) = 0
10x - 4 = 0 10x + 4 = 0
10x = 4 10x = - 4
x₁ = 0,4 x₂ = - 0,4
(х-3)(х+3) \ 4( х-3) = (х+3) \ 4
Смотри решение во вложении