Algebraic Expressions 69
=
−
52
4
=− 13
Step 3. State the main result.− ()−
+=−
15 +
1
13
y+ (^5) (
z
when x = 4, y = (^) − 8 , and z = (^) − 5.
e. xx^2 x− 12
Step 1. Substitute 4 for x in the expression xx^2 x− 12.
xx^2 x− 12 =() (^422) () 4 − 12
Step 2. Simplify the resulting expression.
=()) −()( −^12
2
=−^1641 −^2
=^0
Step 3. State the main result.
xx^2 x− 12 = 0 when x= 4.Problem Evaluate − 25 xx^543 +++ 55 − 337 xx− 7 2 ++x 4 when x=− 1.Solution
Step 1. Substitute x=− 1 for x in the expression − 25 xx^543 +++ 55 − 337 xx− 7 2 ++x 4.− − ++
=− ()+ ()− ()− ()+()−25 + 37 4
2 (− 5 (− 3 (− 7 (− )+ 4
(^543) + 5 3 2
(^5432) + 5 ()( 3 ()( 7 ()(
xx+ 5 xx− 7 x
Step 2. Simplify the resulting expression.
= 25 + + 37 − − 14 +
= 6
Step 3. State the main result.
−^25 + −^37 ++^46 =
xx^543 ++ 55 3 xx− 7 2 x when x=−1.
You can use your skills in evaluating algebraic expressions to evaluate
formulas for given numerical values.
Watch your signs! It’s easy to make careless
errors when you are evaluating negative
numbers raised to powers.