Question 1106436
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(1) You have the coordinates of the center; all you need is the radius.<br>
The radius is the shortest distance from the center to the given line.  The formula for the (shortest) distance from a given point (p,q) to a given line ax+by+c=0 is
{{{abs((ap+bq+c)/sqrt(a^2+b^2))}}}<br>
You can finish from there.<br>
(2) (note: "its", not "it's")<br>
If the roots are 3 and 4, then the function is
{{{f(x) = a(x-3)(x-4)}}} where a is a constant to be determined.<br>
You can find the constant by knowing that y is 6 when x is 5:
{{{a(5-3)(5-4) = 6}}}
{{{a(2)(1) = 6}}}
{{{a = 3}}}<br>
The function is {{{f(x) = 3(x-3)(x-4) = 3(x^2-7x+12) = 3x^2-21x+36}}}<br>
The function opens up.  But you already knew that, since the graph passes through (3,0), (4,0), and (5,6).