Question

Find the equation of a circle with centre (0,0) that passes through (8,-15)

Answer 1

x^2 + y ^2 = r ^2
(substitute the values :D

Answer 2

can yu show me
plug in the values

Answer 3

\[x^2 + y ^2 = r ^2\]
the length of the radius of the circle is \[r=\sqrt{(8)^2+(-15)^2} = 17\]
\[x^2+y^2=289\] <-- is the equation of the circle

Answer 4

lol fine -.-
(8)^2 + (-15)^2 = r^2
64 + 225 = r ^2
289 = r^2
13 = r

Answer 5

where did yu get 17 from

Answer 6

its 13 not 17

Answer 7

nvm its 17

Answer 8

how do yu kno

Answer 9

lol kay hes right its 17

Answer 10

he took the square root of 17

Answer 11

i mean 289

Answer 12

yeh, just look at the answer up there and you will know where the 17 came from, it is the magnitued of the radius, whenever you want to find the magnited of a vector lets say (2,3), it is equal to the square root of the x, y values square.
take a look at this: http://www.mathsisfun.com/algebra/circle-equations.html

Answer 13

), it is equal to the square root of the x, y values SQUARED**