-3,5+V400-7 2/5+K=2015
-35/10+20-37/5+k=2015
-35/10-37/5+20+k=2015
-72+200+k=2015
-128+k=2015
k=2015+128
k=2143
2х-5/4 -6х+1/8=-2
2х-6х=-2+5/4- 1/8
4х=-2+1 1/8
4х=-7/8
х=-7/8:4
x=3 1/2
<span>y=kx+b
{8=k*3+b
{1=k*(-4)+b
-----------------
7=7k </span>⇒ k=1
8=3+b ⇒ b=5
y=x+5
cos(40)/(cos(20)-sin(20))=
=cos(2*20)/(cos(20)-sin(20))=
=(cos^2(20)-(sin^2(20))/(cos(20)-sin(20))=
=((cos(20)-sin(20))(cos(20)+sin(20)/(cos(20)-sin(20))=
=cos(20)+sin(20)