Simultaneous quadratic and linear equations - yr 11

• Mar 30th 2008, 01:08 AM
steph_r
Simultaneous quadratic and linear equations - yr 11
Anyones help would be greatly appreciated...

The graphs: y = x^2 - bx - 14 AND y = -9x + c intersect at
(-1,8) and (-3,10) . Find the values of b and c

Cheers
• Mar 30th 2008, 01:13 AM
Moo
Hello,

I don't know where is b... Nevermind.

You know that the points (-1,8) and (-3,10) belong to both the graphs.
So you just have to replace their values in the expressions of the functions.
• Mar 30th 2008, 01:21 AM
steph_r
Quote:

Originally Posted by Moo
Hello,

I don't know where is b... Nevermind.

You know that the points (-1,8) and (-3,10) belong to both the graphs.
So you just have to replace their values in the expressions of the functions.

im terribly sorry i wrote it wrong.. this is how it was supposed to be written..

y = x^2 + bx - 14 AND y = -9x + c . They intersect at (-1,8) and (-3, 10). Find the values of b and c.

Thank you.
• Mar 30th 2008, 01:30 AM
the wildcat
just substitute (-1,8) and (-3,10) into both equations

e.g.
y=9x+c
at (-1,8)
8= -9 * -1 +c

y=9x+c
at (-3,10)
10= -9 * -3 +c (*=times)