How do you solve #3\leq \frac { - 2x - 3} { 5} < 7#?

1 Answer
Jul 5, 2017

See a solution process below:

Explanation:

First, multiply each segment of the system of inequalities by #color(red)(5)# to eliminate the fraction while keeping the system balanced:

#color(red)(5) xx 3 <= color(red)(5) xx (-2x - 3)/5 < color(red)(5) xx 7#

#15 <= cancel(color(red)(5)) xx (-2x - 3)/color(red)(cancel(color(black)(5))) < 35#

#15 <= -2x - 3 < 35#

Next, add #color(red)(3)# to each segment of the system to isolate the #x# term while keeping the system balanced:

#15 + color(red)(3) <= -2x - 3 + color(red)(3) < 35 + color(red)(3)#

#18 <= -2x - 0 < 38#

#18 <= -2x < 38#

Now, divide each segment of the system by #color(blue)(-2)# to solve for #x# while keeping the system balanced. However, because we are multiplying or dividing inequalities by a negative number we must reverse the inequality operators:

#18/color(blue)(-2) color(red)(>=) (-2x)/color(blue)(-2) color(red)(>) 38/color(blue)(-2)#

#-9 color(red)(>=) (color(red)(cancel(color(black)(-2)))x)/cancel(color(blue)(-2)) color(red)(>) -19#

#-9 color(red)(>=) x color(red)(>) -19#

Or

#x > -19# and #x <= -9#

Or, in interval notation:

#(-19, -9]#