Solve Each System:

x^{2}+ y^{2}= 20

y = x^{2}

This might be a dumb question question, but 20 isn't a square number, so how do i find the radius to graph a circle? Please help!

Printable View

- Dec 21st 2012, 12:06 PMVince604Quadratic-Quadratic Systems Algebraically Question
Solve Each System:

x^{2}+ y^{2}= 20

y = x^{2}

This might be a dumb question question, but 20 isn't a square number, so how do i find the radius to graph a circle? Please help! - Dec 21st 2012, 12:11 PMPlatoRe: Quadratic-Quadratic Systems Algebraically Question
- Dec 21st 2012, 12:31 PMHallsofIvyRe: Quadratic-Quadratic Systems Algebraically Question
No, it doesn't. It has radius sqrt{20}= sqrt{4(5)}= 2 sqrt{5} which is about 4.472.

(Been hitting the eggnog a little early?) - Dec 21st 2012, 12:57 PMSorobanRe: Quadratic-Quadratic Systems Algebraically Question
Hello, Vince604!

Quote:

Solve:

. . x^{2}+ y^{2}= 20 . [1]

. . . . y = x^{2}. . . [2]

Substitute [2] into [1]: .y + y^{2}= 20 . → . y^{2}+ y - 20 = 0

. . . (y - 4)(y + 5) .= .0 . → . y = 4, -5

Substitute into [2]:

. . 4 = x^{2}. → . x =__+__2

. .-5 = x^{2}. No real roots

Therefore: .(x, y) .= .(__+__2, 4)

- Dec 22nd 2012, 10:24 AMVince604Re: Quadratic-Quadratic Systems Algebraically Question