.
1. u =u(x) v=v(x) x, , : (u+v)'=u'+v'. (3)
: y=f(x)=u(x)+v(x).
∆x x ∆u=u(x+∆x)-u(x), ∆v=v(x+∆x)-v(x) u v. y
∆y=f(x+∆x)-f(x)=
=[u(x+∆x)+v(x+∆x)]--[u(x)+v(x)]=∆u+∆v.
,
, (u+v)'=u'+v'.
2. u=u(x) v=v(x) x, . : (uv)'=u'v+uv'. (4)
: y=uv, u v x. x ∆x; u ∆u, v ∆v y ∆y.
y+∆y=(u+∆u)(v+∆v),
y+∆y=uv+u∆v+v∆u+∆u∆v.
, ∆y=u∆v+v∆u+∆u∆v.
∆x→0 , u v ∆x,
3. , , - , ..
(5)
4. , .. y=C, =const, y'=0.
5. , .. y=Cu(x), =const, y'=Cu'(x).