Rules - Brackets

Rules for calculations with parentheses

Count times
in parentheses Parentheses
times
parentheses Minus
brackets
Rule The number
is
multiplied
with
each
term in
the paren-
theses Each term in
one
parentheses
is multiplied by
each term in
the other You can
raise a
minus-
parentheses
by
changing
signs on
all terms
Formula k(a+b)
= ka + kb (a+b)(c+d)
= ac+ad+bc+bd -(a-b)
= -a + b
Example 7(10+2)
= 70+14 (3x – 5)(2x+1)
=6x²+3x-10x–5
= 6x² – 7x – 5 -(x-5)
= -1(x-5)
= -x + 5

English

Dansk

	Count times in parentheses	Parentheses times parentheses	Minus brackets
Rule	The number is multiplied with each term in the paren- theses	Each term in one parentheses is multiplied by each term in the other	You can raise a minus- parentheses by changing signs on all terms
Formula	k(a+b) = ka + kb	(a+b)(c+d) = ac+ad+bc+bd	-(a-b) = -a + b
Example	7(10+2) = 70+14	(3x – 5)(2x+1) =6x²+3x-10x–5 = 6x² – 7x – 5	-(x-5) = -1(x-5) = -x + 5