# Math Help - Equation of a circle

1. ## Equation of a circle

Give the equation of the circle both standard form and general form

Radius 3; tangent to x = -3 and y = 4 and below and to the left of these lines

Please help me and show the solution... Thanks!

2. Hello lance
Originally Posted by lance
Give the equation of the circle both standard form and general form

Radius 3; tangent to x = -3 and y = 4 and below and to the left of these lines

Please help me and show the solution... Thanks!
I'm not entirely sure that I understand the question, but I'm assuming that the circle is to the left of $x = -3$ and below the line $y = 4$. If this is so, then its centre is where:
$x = -3-3=-6$ and $y = 4-3 = 1$
Now the equation with centre $(h,k)$ and radius $r$ has equation:
$(x-h)^2+(y-k)^2 = r^2$
so the equation of this circle is:
$(x+6)^2 + (y-1)^2 = 9$
and when we expand and simplify, this becomes:
$x^2+y^2+12x -2y -28=0$
Grandad