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

Question

 

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

Answer 1

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.

 

Answer 2

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.