Да не за что
-5x+2y=20 |*(-2,5)
2x-5y=-8
12,5x-5y=-50
2x-5y=-8
-5y=-50-12,5x
2x-50-12,5x=-8
-5y=-50-12,5x
-10,5x=42
-5y=-50-12,5*(-4)
x=-4
x=-4
-5y=0
x=-4
y=0
(x,y)=(-4,0)
(2y/(y+b)+(b-y)/y)/((b²+y²)/(b+y))=((2y²+b²-y²)/(y*(y+b))/((b²+y²)/(b+y)=
=((b²+y²)/(y*(b+y))/((b²+y²)/(b+y))=1/y.
1)<span>1- sin2x=cosx-sinx
(сosx-sinx)²-(cosx-sinx)=0
(cosx-sinx)(cosx-sinx-1)=0
cosx-sinx=0/cosx≠0
1-tgx=0⇒tgx=1⇒x=π/4+πn
cosx-sinx-1=0
cos²x/2-sin²x/2-2sinx/2cosx/2-sin²x/2-cos²x/2=0
-2sin²x/2-2sinx/2cosx/2=0
-2sinx/2(sinx/2+cosx/2)=0
sinx/2=0⇒x/2=πn⇒x=2πn
sinx/2+cisx/2=0/cosx/2≠0
tgx/2=-1⇒x/2=-π/4+πn⇒x=-π/2+2πn
2)2(cos x- sin x)²- 5 (sin x - sin x)+2=0
2(cosx-sinx)²=-2
(cosx-sinx)²=-1
нет решения
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