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2.
x - x - 2 = 0
D = 1 - 4*1*(-2) = 1 + 8 = 9
D = 3
x = (1-3)/2 = -2/2 = -1
x = (1+3)/2 = 4/2 = 2

Ответ: -1; 2

x - 5x + 4 = 0
D = 25 - 4*1*4 = 25 - 16 = 9
D = 3
x = (5-3)/2 = 2/2 = 1
x = (5+3)/2 = 8/2 = 4

Ответ: 1; 4

7x - x - 6 = 0
D = 1 - 4*7*(-6) = 1 + 168 = 169
D = 13
x = (1-13)/14 = -12/14 = -6/7
x = (1+13)/14 = 14/14 = 1

Ответ: -6/7; 1

3)
4x - 12  2x + 7
4x - 2x  7 + 12
2x  19
x  19/2
x  9.5

Ответ: (-; 9.5]

3x + 5 gt; 4x - 1
3x - 4x gt; -1 - 5
-x gt; -6
x lt; 6

Ответ: (-; 6)

4)
cos( - ) * sin(/2 - ) - sin(-) = -cos * cos - sin = -cos - sin = - (cos + sin) = -1

sin(/2 - ) - sin( - ) = cos - sina = cos2

(sin8 + sin2)/(cos8 + cos2) = [ 2sin((8a+2a)/2) * cos((8a-2a)/2) ] / [ 2cos((8a+2a)/2) * cos((8a-2a)/2) ] = (sin5 * cos3) / (cos5 * cos3) = sin5/cos5 = tg5

5(1) 
a  (0; /2)  cosa gt; 0
cosa = (1-sina) = (1-4/9) = 5/3

sin2a = 2sinacosa = 2 * 2/3 * 5/3 = 45/9

6(2)
sin2a/2cosa = 2sinacosa/2cosa = sina/cosa = tga

ctga(1 - cos2a) = ctga(1 - cosa + sina) = ctga(sina + sina) = ctga(2sina) = cosa/sina * 4sina = 4cosasina/sina = 4cosasina = (2sinacosa) = sin2a

X-x-2=0
D=b-4ac=1-4*1*(-2)=1+8=9
x1,2=-bD/2a=13/2= -1; 4

x-5x+4=0
D=25-4*4=25-16=9
x1,2=-bD/2a=53/2= 1; 4

7x-x-6=0
D=1-4*7*(-6)=1+168=169
x1,2=-bD/2a=1+13/14= 6/7; 1


4x-122x+7
2x19 :2
x9,5

3x+5gt;4x-1
-xgt;-6 :(-1)
xlt;6