How do you solve #-7c < 28#?

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Answer 1 · 2016-12-30T01:14:06

#c > -4#

We have

#-7c<28#

We divide by #-7# on both sides - and when we do so, we need to reverse the sign:

#(-7c)/(-7)>28/(-7)#

#c > -4#

Let's test this to make sure it's right, by setting #c=0#. In the first equation:

#-7c<28#

#-7(0)<28#

#0<28#

and in the second:

#c > -4#

#0 > -4#

which is correct.

Answer 2 · 2016-12-30T12:39:13

#c > -28/7 = -4#

Add #7c# to both sides and subtract 28 from both sides

#-7c<28#
#color(white)(..)28<7c" "->" "7c" ">" "28#

The other way of doing this is to multiply both sides by (-1) and turn the inequality round the other way

#-7c<28" "->" "(-1)(-7c)>(-1)(+28)#

#" "7c " ">" " -28#
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Divide both sides by 7
#" "c" ">" "-28/7 = -4#