ОБ
Ольга Бровкина
Ответ
1) Степени одинаковые =>
x - 5 = x
-5 = 0 => решений нет
2) y = 0,4xy
1 = 0,4x
x = 1/0,4 = 10/4 = 5/2 = 2,5
3) x1/x2 = 2 => x1 = 2*x2
x^2 + 3x - c = 0
{ x1 + x2 = -3
{ x1 * x2 = -c => c = -(x1 * x2)
2*x2 + x2 = -3 => 3*x2 = -3 => x2 = -1
x1 = 2*x2 = 2*(-1) = -2
c = - (-2) * (-1) = -3
4) x - (2x-7)/3 =< (5x+1)/2
2 * (3x - 2x + 7) =< 3 * (5x + 1)
2x + 14 =< 15x + 3
13x >= 12
x >= 12/13
5) a * b = 210
b = a + 1
a * (a + 1) = 210
a^2 + a - 210 = 0
a(1,2) = (-1 +- 29)/2
a1 = 14
a2 = -15
b = a + 1
b1 = 14+1 = 15
b2 = -15 + 1 = -14
a = 14, b = 15
a = -15, b = -14