complete the square
2007-01-28 15:12:53 · 6 answers · asked by elegant_disaster 1 in Education & Reference ➔ Homework Help
x^2+15x=23
(x^2+15x+56.25)=23+56.25
(x+7.5)^2=79.25
x+7.5=plus or minus square root of 79.25
x~8.9-7.5 or x~-7.5-8.9
x~1.4 or x~-16.4
i'm not sure, but i think that's how you do it if you want to do it the completing the square method
yeah that's right, it's just an approximate answer. depends on how you round.
2007-01-28 15:23:08 · answer #1 · answered by Anonymous · 0⤊ 0⤋
Move stuff around. x2 + 15x = 23
To find the third term, divide the middle term (15) by 2. Put that number in the equation and square it.
x2 + 15x + (15/2)^2 = 23 + (15/2)^2 Because what ever you do to one side of an equation, you must do to the other side.
Now, collapse the left equation.
(x + 15/2)^2 = 23 + 225/4
(x + 15/2)^2 = 92/4 + 225/4
(x + 15/2)^2 = 317/4
Take the square root of both sides.
x + 15/2 = + or - sq rt 317/2
Isolate x.
x = -15/2 + or - 317/2
Multiply the 2 out.
2007-01-28 15:32:09 · answer #2 · answered by huckleberry 5 · 0⤊ 0⤋
x^2 + 15x = 23
x^2 + 15x + 225/4 = 23 + 225/4
(x + 15/2)^2 = 92/4 + 225/4 = 317/4
2007-01-28 15:23:43 · answer #3 · answered by banjuja58 4 · 0⤊ 0⤋
x^2 +15x - 23 = 0. Then use quadratic equation:
(-15 +/- (square root of 15^2 - 4(-23)) ) / 2
I don't have a calculator handy, so you can take it from there.
2007-01-28 15:16:57 · answer #4 · answered by Bobby S 4 · 0⤊ 0⤋
x^2 +15x - 23 = 0
Use the formula X = (-b +/- SQRT(b^2 -4ac))/2a
Hence x = (-15 +/- SQRT(133))/2
2007-01-28 15:20:53 · answer #5 · answered by Orinoco 7 · 0⤊ 0⤋
Sqrt 2 of 23 - 15x. Thanks
2007-01-28 15:16:50 · answer #6 · answered by Anonymous · 0⤊ 0⤋