X+y = (38,5+12,36)/2 + 3(24,39-16,2)
x+y = 50,86/2 + 3*8,19
x+y = 25,43 + 24,57
x+y = 50,00
x²-6x+13=x²-2*3*x+9+4=(x²-2*3*x+3²)+4=(x-3)²+4.
А) 4*a²-3*a+13
б)21*x⁵-3*x⁹
(2sin2x-sin4x)/(sin4x+2sin2x)=(2sin2x-2sin2x·cos2x)/(2sin2x·cos2x+2sin2x)=
=[2sin2x(1-cos2x)]/[2sin2x·(cos2x+1)]=(1-cos2x)/(1+cos2x)=
=(cos²x+sin²x-cos²x+sin²x)/(cos²x+sin²x+cos²x-sin²x)=
=2sin²x/2cos²x=2tg²x