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# if a=3 and b=-2 what is the value of the expression a-2 b-3

if a=3 and b=-2 what is the value of the expression a-2 b-3

### 2 Answers by Expert Tutors

Bruce-Alan M. | Professor BAM (Tutors ALL of Long Island: Nassau + Suffolk)Professor BAM (Tutors ALL of Long Islan...
4.8 4.8 (432 lesson ratings) (432)
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IF your expression "a-2 b-3" is meant to be "(a-2)(b-3)" then Bill is correct, and the answer is -5 when a is 3 and b is -2.

However, if you mean"a - 2b -3" then, substituting the values you gave for a=3 and b=-2, that would be "3 - 2(-2) -3" which is the same as "3 +4 -3" and the expression evaluates to 4.

As in English, punctuation is very important in mathematical expressions:  anything surrounded by parentheses must be evaluated first, to get a number, before any operators outside the parentheses are considered.  Also note that the multiply (or divide) operators are "stronger" and must be evaluated before addition (or subtraction) are considered.

Bill F. | Experienced Teacher & Tutor in Round Rock, TXExperienced Teacher & Tutor in Round Roc...
5.0 5.0 (1 lesson ratings) (1)
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If your expression a-2 b-3 is the same as (a-2)(b-3), which is the same as (a-2) x (b-3):

(3-2)(-2-3) = (1)(-5) = -5   (negative 5)... do what is inside the parentheses first.