Question

How to change signs in subtract questions?

Answer 1

Subtracting a negative number

What sense can we make of

2 − (−5) ?

"2 subtract negative 5."

Let us name the terms. The first term is 2. The second term is −(−5)—for we include the minus sign as part of the name of the term. But

−(−5) = +5.

Lesson 2. Therefore,

2 − (−5)	=	2 + 5
	=	7.

Here is the rule:

a − (−b) = a + b

Any problem that looks like this—

a − (−b)

—rewrite so that it looks like this:

a + b.

That is the only form that the student should have to rewrite.

(Please don't cross out. Rewrite. If you cross out, you can't read the original problem.)

Note again that we use parentheses: a − (−b), to
separate the operation sign − from the algebraic sign − .

and

-a-b = -a+-b