How do you solve #-5 < 1/2(2m + 8) <= 11#?

1 Answer
Nov 22, 2017

See a solution process below:

Explanation:

First, multiply each segment of the system of inequalities by #color(red)(2)# to eliminate the parenthesis while keeping the system balanced:

#color(red)(2) xx -5 < color(red)(2) xx 1/2(2m + 8) <= color(red)(2) xx 11#

#-10 < cancel(color(red)(2)) xx 1/color(red)(cancel(color(black)(2)))(2m + 8) <= 22#

#-10 < 2m + 8 <= 22#

Next, subtract #color(red)(8)# from each segment to isolate the #m# term while keeping the system balanced:

#-10 - color(red)(8) < 2m + 8 - color(red)(8) <= 22 - color(red)(8)#

#-18 < 2m + 0 <= 14#

#-18 < 2m <= 14#

Now, divide each segment by #color(red)(2)# to solve for #m# while keeping the equation balanced:

#-18/color(red)(2) < (2m)/color(red)(2) <= 14/color(red)(2)#

#-9 < (color(red)(cancel(color(black)(2)))m)/cancel(color(red)(2)) <= 7#

#-9 < m <= 7#

Or

#m > -9# and #m <= 7#

Or, in interval notation:

#(-9, 7]#

To graph this we will draw vertical lines at #-9# and #7# on the horizontal axis.

The line at #-9# will be a dashed line because the inequality operator does not contain and "or equal to" clause. The line a #7# will be a solid line because the inequality operator does contain an "or equal to" clause.

We will shade between the two lines to show the interval for the system of inequalities:

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