Exercise 71 Page 74

Practice makes perfect

a We can find the slope m by substituting the given points into the Slope Formula.

m=y_2-y_1/x_2-x_1

SubstitutePoints

Substitute ( 4,- 1) & ( 1,2)

m=- 1- 2/4- 1

SubTerms

Subtract terms

m=- 3/3

CalcQuot

Calculate quotient

m=- 1

b Again, we substitute the given points into the Slope Formula.

m=y_2-y_1/x_2-x_1

SubstitutePoints

Substitute ( 7,3) & ( 5,4)

m=7- 4/3- 5

SubTerms

Subtract terms

m=1/- 2

MoveNegDenomToFrac

Put minus sign in front of fraction

m=- 1/2

c Let's substitute the given points into the Slope Formula.

m=y_2-y_1/x_2-x_1

SubstitutePoints

Substitute ( - 6,8) & ( - 8,5)

m=8- 5/- 6-( - 8)

SubNeg

a-(- b)=a+b

m=8-5/- 6+8

AddSubTerms

Add and subtract terms

m=3/2

d Let's substitute the given points into the Slope Formula.

m=y_2-y_1/x_2-x_1

SubstitutePoints

Substitute ( 55,67) & ( 50,68)

m=67- 68/55- 50

SubTerms

Subtract terms

m=- 1/5

MoveNegDenomToFrac

Put minus sign in front of fraction

m=- 1/5

e To find the correct slope, we should substitute the points into the Slope Formula and simplify.

m=y_2-y_1/x_2-x_1

SubstitutePoints

Substitute ( 1,2) & ( 4,- 1)

m=- 1- 2/4- 1

SubTerms

Subtract terms

m=- 3/3

CalcQuot

Calculate quotient

m=- 1

The correct slope is - 1. The mistake Azizah made is that she lost the minus sign. Perhaps she substituted 2-(- 1) in the numerator instead of -1 -2.

Subchapter links

2.2.1 Slope as Motion p.64-65

2.2.2 Rate of Change p.70-71

2.2.3 Equations of Lines in Situations p.74-75

Exercise 71 Page 74

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