No idea what I'm doing here

kasey

New member
I have no idea what I'm doing on these two problems:

The function f(x) = 25x + 400 represents Jason's total savings after x weeks. How much as he saved after 8 weeks?

Suppose y varies directly as x and y = 27 when x = 3. Find x when y = 45

Write the point-slope form of an equation for the line passing through the point at (3,-6) with slope -4/3

Deteremine whether the relation {(3,2), (4,5), (-3,5),(-4,2)} is a function.

Can somebody please explain how to do these?
step by step would be greatly apperciated

skeeter

Senior Member
kasey said:
I have no idea what I'm doing on these two problems:

two? looks like four to me ... no wonder you're having problems

The function f(x) = 25x + 400 represents Jason's total savings after x weeks. How much as he saved after 8 weeks?

the question is asking for f(8) ... just substitute 8 in for x in the function and determine his total savings

Suppose y varies directly as x and y = 27 when x = 3. Find x when y = 45
y varies directly as x as an equation is y = kx, where k is a constant.
the problem says y = 27 when x = 3 ... so what is k?

k stays the same ... substitute 45 for y in the same equation and determine x

Write the point-slope form of an equation for the line passing through the point at (3,-6) with slope -4/3

point-slope form is y - y<sub>1</sub> = m(x - x<sub>1</sub>)
where (x<sub>1</sub>,y<sub>1</sub>) is the given point and m is the slope

Deteremine whether the relation {(3,2), (4,5), (-3,5),(-4,2)} is a function.
what's the definition of a function? look it up in your textbook.

Can somebody please explain how to do these?
step by step would be greatly apperciated