Through (3, 4) and perpendicular to y = (1/3)x - 3

3

x

−

2

y

=

7

Explanation:

Write the standard form of the line that goes through  

(

3

,

1

)

and is perpendicular to  

y

=

−

2

3

x

+

4

.

The equation  

y

=

−

2

3

x

+

4

is in slope intercept form

y

=

m

x

+

b

where  

m

= slope and  

b

= the  

y

intercept.

The slope of this line is then  

m

=

−

2

3

A perpendicular slope is the opposite sign reciprocal. So, we change the sign of  

−

2

3

and switch the numerator and denominator.

Perpendicular slope  

m

=

3

2

To find the equation of the new line, use the point slope equation

y

−

y

1

=

m

(

x

−

x

1

)

where  

m

=

slope and  

(

x

1

,

y

1

)

is a point.

The slope is  

3

2

and the point is the given point  

(

3

,

1

)

.

y

−

1

=

3

2

(

x

−

3

)

a

a

a

Distribute

y

−

1

=

3

2

x

−

9

2

Standard form is  

a

x

+

b

y

=

c

where  

a

,

b

and

c

are integers and  

a

is positive.

a

a

2

(

y

−

1

=

3

2

x

−

9

2

)

a

a

a

Multiply the equation by  

2

a

a

a

a

a

2

y

−

2

=

3

x

−

9

−

3

x

a

a

a

a

a

a

a

−

3

x

a

a

a

Subtract  

3

x

from both sides

−

3

x

+

2

y

−

2

=

−

9

a

a

a

a

a

a

a

a

+

2

a

a

a

+

2

a

a

a  Add  2  to both sides  − 3 x + 2 y = − 7 − 1 ( − 3 x + 2 y = − 7 ) a a a Multiply the equation by  − 1 3 x − 2 y = 7

step-by-step explanation:

30% of $420 is 0.30($420) = $126 and $420 + $126 = $546.

or, 130% of $420 is 1.3($420) = $546.

notice that this is not the $600 original list price with which we started.

why doesn't this work?

the method does not work because 30% of $420 is not the same amount as the 30% of $600. it may seem obvious when stated this way, but it is a very common error made on problems of this type. we cannot just use the same percent and get back to the original amount because we are taking that percent of a different value.

to work problems of this type correctly, it is generally best to write an equation for the situation and then solve.

example: since (100% – 30%)(original price) = (sale price)

70% of the   (original price) is $420.

0.7x   = 420

equation image indicator

x = 600

the original cost was $600.

we may also solve this problem using the two-step method. working the problem in two steps requires us to use more algebra skills. we have to know that x = 1x (identity property of multiplicationtext annotation indicator) and that 1x – 0.3x = 0.7x (subtracting like terms). then we solve the problem as follows:

(original price) – 30%(original price) = sale price

x – 0.3x = 420

0.7x = $420

equation image indicator

x = 600

the original cost was $600.  

note that with both of the above methods we do obtain the correct original amount.

example: after a 5% pay raise, hermione is earning $22,680 per year. what was she earning before the pay raise?

105% of (original salary) = current salary

1.05x = 22,680

equation image indicator

x = 21,600

hermione earned $21,600 per year before the pay raise.

this is an example so maybe you will get how to at least do it!

it is not that hard all u have to do is plot the graph

step-by-step explanation: