Срочно , кроме 5-ого . Спасибо

1. x⁴-65x+64=0 Пусть  x²=t>0   ⇒ t²-65t+64=0   D=3969 t₁=64   x²=64   x₁=8    x₂=-8 t₂=1     x²=1     x₃=1    x₄=-1. 2. 3x²-5x-2≤0 3x²-5x-2=0   D=49 x₁=-1/3     x₂=2   ⇒ (x+1/3)(x-2)≤0 -∞________+_______-1/3_______-_______2________+________+∞ x∈[-1/3;2]. 3. x²+y²-13=0         x²+y²-13=0      x²+y²=13     xy-6=0  |×2         2xy-12=0         2xy=12 Суммируем эти уравнения: x²+2xy+y²=25 (x+y)²=25 x+y=5                                                      x+y=-5 y=5-x                                                       y=-5-x x(5-x)-6=0                                               x(-5-x)-6=0 5x-x²-6=0                                                -5x-x²-6=0 x²-5x+6=0  D=1                                       x²+5x+6=0   D=1 x₁=3        x₂=2                                     x₃=-3          x₄=-2 y₁=2        y₂=3                                     y₃=-2          y₄=-3.