Posted by **John** on Wednesday, April 23, 2008 at 9:49pm.

solve for X 30y=x^2-14x+13

- Math -
**Damon**, Wednesday, April 23, 2008 at 9:56pm
x^2 - 14 x + 13 = 30 y

x^2 - 14 x = 30 y - 13

x^2 - 14 x + 49 = 30 y + 36

(x-7)^2 = 30 y + 36

x - 7 = +/- sqrt (30 y + 36)

x = 7 +/- sqrt (30 y + 36)

- Math -
**Damon**, Wednesday, April 23, 2008 at 10:02pm
This is so much harder than your other question that I suspect a typo by the way.

- Math -
**John**, Wednesday, April 23, 2008 at 10:05pm
x^2 - 14 x + 13 = 30 y

x^2 - 14 x = 30 y - 13

x^2 - 14 x + 49 = 30 y + 36 ****

(x-7)^2 = 30 y + 36

x - 7 = +/- sqrt (30 y + 36)

x = 7 +/- sqrt (30 y + 36)

where did you get the 49 or 36

- Math -
**Damon**, Wednesday, April 23, 2008 at 10:10pm
Completing the square

x^2 + a x = something

x^2 + a x + (a/2)^2 = something + (a/2)^2

so

if

x^2 -14 x = something

then

x^2 - 14 x +(14/2)^2 = something + (14/2)^2

or

x^2 - 14 x + 49 = something + 49

(x-7)^2 = something + 49

x - 7 = +/- sqrt (something + 49)

by taking half the second coefficient and squaring it, I get a perfect square.

- Math -
**Damon**, Wednesday, April 23, 2008 at 10:13pm
and 49 - 13 = 36

- Math -
**JOHN**, Wednesday, April 23, 2008 at 10:24pm
why is this not correct

30y = x^2 - 14x + 13

- 13

30y - 13 = x^2 - 14x

_________ ___________

-14 -14

x = sqrt 30y-13

_______

-14

Im really trying to follow your work... This is what I got the first time I tried before i asked...

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