How do you solve #2x+22=0# by graphing?

1 Answer
Jul 17, 2018

Answer:

Plot the graph of #(2x+22)#.
The solution is the value of #x# where the line crosses the #x# axis.

Explanation:

It is very easy to solve this by using algebra, but if you need to solve it by graphing then:

Plot the graph of #(2x+22)#.
The solution is the value of #x# where 2#x#+22 = 0 (i.e. where the line crosses the #x# axis).

You can do this with a graphic calculator or computer, or you can do it on paper as follows:

Put values for #x# into the left hand side of the eqn
(#2x+22#) ....(you should recognize this as a straight line)

and plot them as the #y# value on a graph

e.g.
if #x# = 0, #y = (2*0)+22 = 22# so plot the point (0,22)
if #x# = 4, #y = (2*4)+22 = 30# so plot the point (4,30)
if #x# = -6, #y = (2*-6)+22 = 10# so plot the point (-6,10)

Draw a straight line through these points:
graph{2x+22 [-41.3, 38.7, -5.58, 34.42]}

The line shows all the values of #2x+22# (read on #y# axis) for all values of #x# (#x# axis)

We are interested in the value of #x# when #2x+22=0#, so read the value of #x# at #y = 0# (where the line crosses the #x# axis).

Looks like it's #x=-11#

(We can check this by using #x= -11# in the expression 2#x#+22 and verifying that it is equal to 0 for this value of #x#)

#2*-11+22= -22 + 22 = 0#

The plot of #x=-11# on a graph is a vertical line through x=-11
graph{-1000x-11000 [-41.3, 38.7, -5.58, 34.42]}