How do you solve |7 - 6x| <= -4?

1 Answer
Aug 30, 2016

x >= +11/6 or x <=1/2

Set the +value <= -4 and -"value" <= -4 and solve.

Explanation:

The absolute value can be either a negative or a positive value. It is the distance from the value to zero. So the answer that comes out is the same regardless if the answer inside is negative or positive.

Set +1 xx ( 7 - 6x) <= -4 and solve for the positive value.

This gives

7- 6x <= -4 " " subtract -7 from both sides.

7-7 - 6x <= -4 -7" " This gives

-6x <= -11 " " divide everything by -1 . The sign will change.

(- x)/-1 >= (-11)/(6xx-1)" " This gives

x >= + 11/6

( -1)/-1 = +1 the opposite of -a - is +a (Dividing by a negative always gives you the opposite of what you start with)

When you divide an inequality by a negative number the inequality sign in the middle changes around.

(-11)/(-1 xx6) = + 11/6 (Dividing by a negative always gives you the opposite sign of what you start with)

Then set -1( 7-6x ) <= -4" " and solve for x .This gives

-7 + 6x <= -4" " add seven to both sides

-7 +7 + 6x <= -4 + 7 " " this gives

6x <= + 3 " " Divide both sides by 6

(6x)/6<= +3/6" " this gives

x <= 1/2

Note that as the x is positive, dividing by +1 would not change any of the values, so is not necessary.