# quick algebric question...important!

• Mar 8th 2009, 10:03 PM
KAS
quick algebric question...important!
Hi everyone..I have a question which was troubling me somwhow..
when I try to sketch the functions on a graph, I keep on getting lines which don't cut each other..
this is the question:

On a graph, plot the line y = 80 + 10x and y = 34x – x2. Mark clearly the y-intercept, x-intercepts, x-axis and y-axis.
Find the values of x where the two curves intersect.

• Mar 8th 2009, 10:35 PM
Chris L T521
Quote:

Originally Posted by KAS
Hi everyone..I have a question which was troubling me somwhow..
when I try to sketch the functions on a graph, I keep on getting lines which don't cut each other..
this is the question:

On a graph, plot the line y = 80 + 10x and y = 34x – x2. Mark clearly the y-intercept, x-intercepts, x-axis and y-axis.
Find the values of x where the two curves intersect.

For the second equation, do you mean $y=34-x^2$? If so, the two functions are graphed like this:

http://img.photobucket.com/albums/v4.../mhfquest2.jpg

If not, then you probably mean $y=34-2x$. The graph of the two lines is this:

http://img.photobucket.com/albums/v4...1/mhfquest.jpg

Can you take it from here and complete the problem?
• Mar 8th 2009, 11:25 PM
KAS
aha thanx a lot:)
I'll try ask my tutor if the function he gave was wrong or not..
n then will c ..
but if it was the first graph, does that mean that the intersection will be equal to zero?
• Mar 9th 2009, 09:29 AM
sammy28
if you write out a table of values for $y=34x-x^2$ then plot you should find a solution graphically.

x -3, -2, -1, 0, 1, 2, 3,
y -111, -72, -35, 0, 33, 64, 93

since

$80 + 10x = 34x - x^2$

$x^2 - 24x + 80 = 0$

$(x-4)(x-20) = 0$

x = 4 and 20 (x,y) = (4,120) and (20,280)
• Mar 9th 2009, 11:35 AM
c_o_d
Quote:

Originally Posted by Chris L T521
For the second equation, do you mean $y=34-x^2$? If so, the two functions are graphed like this:

http://img.photobucket.com/albums/v4.../mhfquest2.jpg

If not, then you probably mean $y=34-2x$. The graph of the two lines is this:

http://img.photobucket.com/albums/v4...1/mhfquest.jpg

Can you take it from here and complete the problem?

Dear chris hi,

The equations which you wrote them are not correct ... they are :
$y=34x-2x$
or
$y=34x-x^2$ ..

bye