Find the equation of the circle with center (-1,7) and radius 2 .
a. x ^2 + 2x + y ^2 - 28y + 50 = 0
b. x ^2 - 2x - y ^2 - 14y - 48 = 0
c. x ^2 + 14x + 48 + y ^2 - 2y = 0
d. x^ 2 - 14x + 48 + y ^2 - 2y = 0
e. x ^2 + 2x + y ^2 - 14y + 48 = 0
2007-09-02 04:49:32 · 7 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
(x + 1) ² + (y - 7) ² = 4
x ² + 2 x + 1 + y ² - 14 y + 49 = 4
x ² + 2 x + y ² - 14 y + 46 = 0
Option e is closest
2007-09-06 04:26:43 · answer #1 · answered by Como 7 · 0⤊ 0⤋
The center is -1, so the only possible correct choices are ones with:
x^2 + 2x ....
So we only try out choices a. and e.
a. is wrong though because the center is 7, so we need something like:
y^2 - 14y ...
e. should have been the only possible answer, but look at this.
x^2 + 2x + y^2 - 14y + 48 = 0
x^2 + 2x + 1 + y^2 - 14x + 48 = 1
x^2 + 2x + 1 + y^2 - 14x + 49 = 2
(x+1)^2 + (y-7)^2 = 2
2, should have been (radius)^2, but not (radius)
The rest are correct, because the center is
(-1,7)
The equation of a circle is: (x-h)^2 + (y-k)^2 = r^2
The radius is still wrong so....
NO ANSWER!!!!!!!!!!!!!!!!!
2007-09-02 12:01:11 · answer #2 · answered by UnknownD 6 · 0⤊ 0⤋
a) simplifies to (x + 1)² + (y - 14)² = 147
b) x ^2 - 2x - y ^2 - 14y - 48 = 0 is not a circle
c) simplifies to (x + 7)² + (y - 1)² = 2
d) simplifies to (x - 7)² + (y - 1)² = 2
e) simplifies to (x + 1)² + (y -7)² = 2
in general the equation for a circle is:
(x - h)² + (y - k)² = r² where r is the radius and the center is at the point (h, k)
equation e has the correct center, but not the correct radius.
2007-09-06 03:35:06 · answer #3 · answered by Merlyn 7 · 0⤊ 0⤋
(x+1)^2 + (y-7)^2 = 2^2
x^2+2x+1 +y^2-14y +49 =4
x^2+2x +y^2-14y +46= 0 <-- Correct answer
So the answer is none of the above.
2007-09-02 12:09:45 · answer #4 · answered by ironduke8159 7 · 0⤊ 0⤋
After substituting the given values, expand the standard form of an equation of a circle (which is radius-center form) in the form (x-h)^2+(y-k)^2=r^2 where (h,k) is the center and r is the radius.
This portion of yahoo is not a quiz portion so your question is rather inappropriate for this section. It is something that can be learned from a standard precalculus text book. Grab one.
2007-09-02 12:02:25 · answer #5 · answered by Anonymous · 0⤊ 1⤋
(x+1)^2+(y-7)^2=2^2
x^2+y^2+2x-14y+46=0
¡Ninguna!
Saludos.
2007-09-02 11:56:24 · answer #6 · answered by lou h 7 · 0⤊ 0⤋
try doing your howmework next time.
2007-09-02 11:52:54 · answer #7 · answered by X_nOmAd_oo57-ha 3 · 0⤊ 2⤋