Answer:
Evaluating Expressions on MathHelp.com
Evaluating Expressions
Usually the only hard part in evaluation is in keeping track of the "minus" signs. I would strongly recommend that you use parentheses liberally, especially when you're just getting started.
Evaluate a2b for a = –2, b = 3, c = –4, and d = 4.
To find my answer, I just plug in the given values, being careful to use parentheses, particularly around the "minus" signs. Especially when I'm just starting out, drawing the parentheses first may be helpful:
a2 b
( )2 ( )
(–2)2 (3)
(4)(3)
12
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Note how using parentheses helped me keep track of the "minus" sign on the value of a. This was important, because I might otherwise have squared only the 2, ending up with –4, which would have been wrong.
By the way, it turned out that we didn't need the values for the variables c and d. When you're given a big set of expressions to evaluate, you should expect that there will often be one or another of the variables that won't be included in any particular exercise in the set.
Evaluate a – cd for a = –2, b = 3, c = –4, and d = 4.
In this exercise, they've given me extra information. There is no b in the expression they want me to evaluate, so I can ignore this value in my working:
(–2) – (–4)(4)
–2 – (–16)
–2 + 16
16 – 2
14
