sin2a=2sinacosa=-2*3*4/25=-24/25
sina=3/5 cosa=-4/5
tga/2=sina/(1-cosa)=sqrt(3)/2(1+1/2)=sqrt(3)/3
cosa=-1/2
1) x-3y+(x-3y)(x+3y)
2) (3m+n-5)(3m+n+5)
3) 1-(x(2) -10xy+256(2)) = 1-(x-5y)(2)
32 - 4X = X^2
X^2 + 4X - 32 = 0
D = 16 + 128 = 144 ; V D = 12
X1 = ( - 4 + 12 ) : 2 = 4
X2 = ( - 16 ) : 2 = ( - 8 )
3) (30.000* 0.40) = 12.000
12.000 + 30.000тыс = всего 42 тыс