Sin7π/12-sinπ/12=2sinπ/4cosπ/3=2*√2/2*1/2=√2/2
3(1-2x)/2(x²+2x+4) *(2x+1)/(2-x)²*(5-x)(4+2x+x²)/(2x-1)(2x+1)=-3/2(2-x)=3/2(x-2)
( Х + 10) / 4 + ( Y - 2) / 3 = 1
3*( X + 10) + 4 *( Y - 2) = 12
3X + 30 + 4Y - 8 = 12
3X + 4Y = - 10
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3X - Y = 25
Y = 3X - 25
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3X + 4*( 3X - 25) = - 10
3X + 12X - 100 = - 10
15X = 90
X = 6
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Y = 18 - 25 = ( - 7 )
Знак системы не пишу.
2x+y=9 y=9-2x y=9-2x x=5 x=5
3x-5y=20 3x-45+10x=20 13x=65 y=9-10 y=-1
x+2y=7 x=7-2y
5x-y=2 5(7-2y)-y=2
Дальше сам)