(x+y)(x+y)=16
x^2+y<span>^+2xy=16
xy=3
x=3/y
9/y</span>^2+y<span>^=10
y</span>^4-10y<span>^2+9=0
y</span>^2=9 i y^=1 poetomeu x^2=1 i x<span>^2=9</span><span>
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(3а²-27)/(18-6а)=3*(а²-9)/(6*(3-а))= (а-3)(а+3)/(2(3-а))= (а-3)(а+3) / ((-2)*(а-3))= (а+3)/(-2)= - (а+3)/2
Sin20*sin40*sin80=sin20*sin(2*20)*sin(2*40)
sin20*2sin20*cos20*2sin40*cos40