Vivian L. answered • 12/18/13

Tutor

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Microsoft Word/Excel/Outlook, essay composition, math; I LOVE TO TEACH

Hi Mik;

FIRST QUESTION...

slope=m=(y-y

_{1})/(x-x_{1})m=(1-2)/(-6-4)=-1/-10=1/10

The slope-intercept formula is...

y=mx+b

y=(1/10)x+b

Let's plug-in one coordinate...

1=(1/10)(-6)+b

1=(-6/10)+b

Let's add 6/10 to both sides...

1+(6/10)=(-6/10)+b+(6/10)

1 6/10=b

1 3/5=b

The formula is...

y=(1/10)x+(1 3/5)

Let's plug-in the other coordinate to see verify the results...

y=(1/10)x+b

2=(1/10)(4)+b

2=(2/5)+b

Let's subtract 2/5 from both sides...

2-(2/5)=(2/5)+b-(2/5)

1 3/5=b

y=(1/10)x+(1 3/5)

Same results!

slope is 1/10

y-intercept, value of y when x=0, is 1 3/5

SECOND QUESTION...

slope=m=(y-y

_{1})/(x-x_{1})m=(-4-6)/(-8-7)

m=-10/-15=2/3

y=mx+b

y=(2/3)x+b

Let's plug-in one coordinate...

-4=(2/3)(-8)+b

-4=(-16/3)+b

For convenience, let's convert the 4 into 3rds...

-12/3=(-16/3)+b

Let's add (16/3) to both sides...

(16/3)-(12/3)=(-16/3)+b+(16/3)

4/3=b

1 1/3=b

y=(2/3)x+ 1 1/3

Other coordinate...

6=(2/3)(7)+ b

6=(14/3)+b

18/3=(14/3)+b

4/3=b

1 1/3=b

y=(2/3)x+ 1 1/3

Results are identical!

Slope is 2/3.

y-intercept, value of y when x=0, is 1 1/3.