Answer:
Part 1) The radius is [tex]r=17\ units[/tex]
Part 2) The points (-15,14) and (-15,-16) lies on the circle
Step-by-step explanation:
The correct question is
A circle is centered at the point (-7, -1) and passes through the point (8, 7).
The radius of the circle is ____units.
The point (-15,
?) ) lies on this circle
step 1
Find the radius of the circle
we know that
The distance from the center to any point on the circumference is equal to the radius.
we have
[tex](-7,-1),(8,7)[/tex]
Find the distance
the formula to calculate the distance between two points is equal to
[tex]d=\sqrt{(y2-y1)^{2}+(x2-x1)^{2}}[/tex]
substitute
[tex]r=\sqrt{(7+1)^{2}+(8+7)^{2}}\\r=\sqrt{(8)^{2}+(15)^{2}}\\r=\sqrt{289}\\r=17\ units[/tex]
step 2
The point (-15,y) lies on the circle
we know that
If a ordered pair lie on the circle, them the ordered pair must satisfy the equation of the circle
The equation of the circle is
[tex](x-h)^{2}+(y-k)^{2}=r^{2}[/tex]
The center is (-7,-1) an the radius is 17 units
substitute
[tex](x+7)^{2}+(y+1)^{2}=17^{2}\\(x+7)^{2}+(y+1)^{2}=289[/tex]
substitute the x-coordinate of the point and solve for the y-coordinate
For x=-15
[tex](-15+7)^{2}+(y+1)^{2}=289\\(-8)^{2}+(y+1)^{2}=289\\64+(y+1)^{2}=289\\(y+1)^{2}=289-64\\(y+1)^{2}=225[/tex]
square root both sides
[tex](y+1)=\pm15\\y=-1\pm15\\y=-1(+)15=14\\y=-1(-)15=-16[/tex]
therefore
The points (-15,14) and (-15,-16) lies on the circle
see the attached figure to better understand the problem
