X^2 - 2x + 1 = 29 - 5x
x^2 + 3x - 28 =0
D = b^2 - 4ac = 9 + 112 = 121 = 11^2
x1 = ( - 3 + 11) / 2 = 4
x2 = ( - 3 - 11) / 2 = - 7
5x - 10 = 3x^2 - 4x - 4
- 3x^2 + 9x - 6 = 0
x^2 - 3x + 2 = 0
D = b^2 - 4ac = 9 - 8 = 1
x1 = ( 3 + 1)/2 = 2
x2 = ( 3 - 1) / 2 = 1
7(x^2 + 2x) = 2( x^2 + 24)
7x^2 + 14x = 2x^2 + 48
7x^2 - 2x^2 + 14x - 48 = 0
5x^2 + 14x - 48 = 0
D = b^2 - 4ac = 196 + 960 = 1156 = 34^2
x1 = ( - 14 + 34) / 10 = 2
x2 = ( - 14 - 34) / 10 = - 4,8
2cos2x = 4sin(π/2 + x) + 1
2cos2x = 4cosx + 1
4cos²x - 2 = 4cosx + 1
4cos²x - 4cosx - 3 = 0
4cos²x + 2cosx - 6cosx - 3 = 0
2cosx(2cosx + 1) - 3(2cosx + 1) = 0
(2cosx + 1)(2cosx - 3) = 0
1) 2cosx + 1 = 0
2cosx = -1
cosx = -1/2
x = ±2π/3 + 2πn, n ∈ Z
2) 2cosx - 3 = 0
2cosx = 3
cosx = 3/2 - нет корней, т.к. cosA ∈ [-1; 1]
Ответ: x = ±2π/3 + 2πn, n ∈ Z.
Sn=(b1*(1-q^n))/1-q
b1=36
b2=-18,9
q=b2/b1=-18,9/36
q=-0,525
n=8
S8=(36*(1-(-0,525)^8)/1-(-0,525)
S8=(36*0,994)/1,525=23,4703
90-1,2,3,5,6,9,10,15,18,30,
45,90
2*(3а-4+5)=6а-8+10=6а+2
1) 2*3а=6а
2)2*4=8
3)2*5=10