Sin²a+cos²a=1
cosa=√1-sin²a=√1-1/5 = √4/5=2/√5
1+tg²a=1/cos²a ⇒ tga= √ 1/cos²a-1 = √ 5/4 - 1 = √ 1/4 = 1/√4
3-3(x+2)=5-4x
3-3х+6=5-4х
-3х+4х=5-3-6
Х=-8
Ответ: Х=-8
2X + 2Y = 14
2( X + Y) = 7*2
X + Y = 7
Y = 7 - X
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XY = 12
X*(7 - X) = 12
7X - X^2 = 12
- X^2 + 7X - 12 = 0
D = 7^2 - 4 * (-1)* (-12) = 49 -4*12 = 49 - 48 = 1
X1 = (-7 + 1) \ - 2 = - 6 \ - 2 = 3
X2 = (-7 - 1) \ - 2 = - 8 \ - 2 = 4
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Y1 = 7 - 3 = 4
Y2 = 7 - 4 = 3
16(25c^2+70c+49)-81=0
400c^2+1120c+784-81=0
400c^2+1120c+703=0
D=1120^2-4*400*703=1254400-1124800=129600=360^2
x1=(-1120-360):800=-1.85
x2=(-1120+360):800=-0.95
Ответ: -1,85 и -0,95