Big Ideas Math Integrated I, 2016
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Big Ideas Math Integrated I, 2016 View details
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Exercise 4 Page 47

First isolate the absolute value on one side of the equation.

Solutions: x=9 and x=-3

Practice makes perfect
Before we can solve the given equation, we need to isolate the absolute value expression using the Properties of Equality.
2|x-3|-5=7
2|x-3|-5+5=7+5
2|x-3|=12
|x-3|=6
An absolute value is always a non-negative number because it measures the expression's distance from a midpoint on a number line. |x-3|= 6This equation means that the distance is 6, either in the positive direction or the negative direction. |x-3|= 6 ⇒ lx-3= 6 x-3= -6 We need to solve both of these cases so that we can find both values that satisfy the equation.
| x-3|=6

lc x-3 ≥ 0:x-3 = 6 & (I) x-3 < 0:x-3 = - 6 & (II)

lcx-3=6 & (I) x-3=-6 & (II)

(I), (II): LHS+3=RHS+3

lx= 9 x= -3
After solving an absolute value equation, it is necessary to check for extraneous solutions. To do this, we substitute the found solutions into the given equation and determine if a true statement is made.
2|x-3|-5=7
2|{\color{#0000FF}{9}}-3|-5\stackrel{?}=7
Simplify equation
2|6|-5\stackrel{?}=7
2\cdot 6 -5\stackrel{?}=7
12-5\stackrel{?}=7
7=7 ✓
Substituting 9 for x in the equation does result in a true statement, so x=9 is not an extraneous solution. Now let's check whether or not x=- 3 is extraneous.
2|x-3|-5=7
2|({\color{#FF0000}{\text{-} 3}})-3|-5\stackrel{?}=7
Simplify equation
2|\text{-} 6|-5\stackrel{?}=7
2\cdot 6 -5\stackrel{?}=7
12-5\stackrel{?}=7
7 = 7 ✓
Substituting (- 3) for x in the equation also does result in a true statement, so x=- 3 is not an extraneous solution. Therefore, the equation has two solutions.