b	f(x) dx = -		a	f(x) dx
	a			b

	a	f(x) dx = 0
	a

	b	f(x) dx =		c	f(x) dx +		b	f(x) dx
	a			a			c

	b	f1(x) + f2(x) + ... + fn(x) dx =
	a

		=		b	f1(x) dx +		b	f2(x) dx + ... +		b	fn(x) dx
				a			a			a

	b	k· f(x) dx = k·		b	f(x) dx
	a			a