How do you solve 12x+132=12x-10012x+132=12x100 by graphing?

1 Answer
Jan 23, 2017

Is this question correct?

There is no common point so no solution to this system of equations as presented.

Explanation:

color(blue)("Important point to note before we start")Important point to note before we start

Given: 12x+132=12x-10012x+132=12x100

Subtract 12x12x from both sides

132=-100 color(red)(larr" This is untrue so no solution")132=100 This is untrue so no solution

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color(blue)("Answering the question as if there is a system of equations")Answering the question as if there is a system of equations

In circumstances such as this you would set both as equal to yy so that you have the format of:

12x+132=y_1=12x-100 color(red)(larr" This proves to be false")12x+132=y1=12x100 This proves to be false

However, take a closer look at it. Notice that they both have

12x+" some constant"12x+ some constant

Now consider the standardised form:

y=mx+cy=mx+c where mm is the gradient.

y_2=12x+132" "y_3=12x-100y2=12x+132 y3=12x100
y=mx+c" "y=mx+cy=mx+c y=mx+c

The gradient of mm is the same in both equations. So they both have the same gradient (slope)

color(red)("They are parallel")They are parallel

As they have different starting points on the y-axis ( y-intercept ) they do not share a common point anywhere.

color(red)("Thus there is no solution")Thus there is no solution

Tony B