A18=a1+17d=70+17*(-3)=19
Ответ: 19
<span>1,2x - 0,5x^2 = 4x^2 - 0,8x
2x - 4,5x^2 = 0
45x^2 - 20x = 0
9x^2 - 4x = 0
x(9x - 4) = 0
x =0
or
x = 4/9
0,6x^2 + V3x = 0
x(0,6x + V3) = 0
x =0
or
x = -5V3/3(V- корень)
9x^2 - 10x = 7x^2 - 15x
2x^2 + 5x = 0
x(2x + 5) = 0
x = 0
x = -2,5
2/3x^2 = 5x
2x^2 - 15x = 0
x(2x - 15) = 0
x = 0
x = 7,5</span>
60 / x = 66 / x + 2,
60 / x - 66 /x = 2,
- 6 / x = 2,
- 6 = 2x,
2x = - 6,
x = - 6 / 2,
x = - 3,
2)положительный3)отрицательный