# help with circle and points on a line

• Oct 8th 2008, 05:39 PM
NeedHelp18
help with circle and points on a line
1) Find the values of a and b if (3a + 11, 2b - 5) = (3,-2).
Do I have have to substitue 3 into a, and -2 into b???

2) Find an equation for the given points on a line (-2,-3) and (5,-4).
Is it y= -1/7(x) - 23/7?

3) Find an equation of a circle with center (-2,-3) tangent to the line y=7.
• Oct 8th 2008, 06:19 PM
Jhevon
Quote:

Originally Posted by NeedHelp18
1) Find the values of a and b if (3a + 11, 2b - 5) = (3,-2).
Do I have have to substitue 3 into a, and -2 into b???

no.

notice the colors: $({\color{red}3a + 11}, {\color{blue}2b - 5}) = ({\color{red}3}, {\color{blue}-2})$

now do you see what to do?

Quote:

2) Find an equation for the given points on a line (-2,-3) and (5,-4).
Is it y= -1/7(x) - 23/7?
yes

Quote:

3) Find an equation of a circle with center (-2,-3) tangent to the line y=7
the equation of a circle with center $(h,k)$ and radius $r$ is given by:

$(x - h)^2 + (y - k)^2 = r^2$

we want this circle to touch the line $y = 7$ at one point. think of how large the radius must be to touch the line $y = 7$
• Oct 8th 2008, 06:32 PM
NeedHelp18
ok i hope this is right...

is it

(x + 2)^2 + (y + 3)^2 = 100
• Oct 8th 2008, 06:34 PM
Jhevon
Quote:

Originally Posted by NeedHelp18
ok i hope this is right...

is it

(x + 2)^2 + (y + 3)^2 = 100

yes