4(x+5)=-8
4x+20=-8
4x=-8-20
4x=-28
x=-7
-(x+4)=-2x
-x-4=-2x /×(-1)
x+4-2x=0
-x=-4
x=4
5(2-2x)=5
10-10x=5
10x=5
x=5/10
x=0.5 или 1/2
4(x+1)-3x=2x
4x-3x-2x+4=0
-x=-4
x=4
При а = 3:
(5а² - 20а²) - (4а³ - 18а²) = (5*3² - 20*3²) - (4*3³ - 18*3²) = (5*9 - 20*9) - (4*27 - 18*9) = (45 - 180) - (108 - 162) = - 135 - 54 = -189
Решение
Cos2x=1+sinx
1 - 2sin²x - sinx = 1
sinx(2sinx + 1) = 0
1) sinx = 0
x₁ = πk, k∈Z
2) 2sinx + 1 = 0
sinx = - 1/2
x = (-1)^n *arcsin(- 1/2) + πn, n∈Z
x = (-1)^(n + 1) *arcsin(1/2) + πn, n∈Z
x₂ = (-1)^(n + 1) *(π/6) + πn, n∈Z
<span>Ответ: x₁ = πk, k∈Z ; x₂ = (-1)^(n + 1) *(π/6) + πn, n∈Z</span>