Posted by **Algebra** on Wednesday, May 27, 2009 at 9:35am.

can show me how to do this with out just squaring

3x^(1/2) - x - 6 = 0

how do i do this and solve for x with out just squareing and using quadratic formula. I was never taught the proof of the quadratic formula and would like to know how to do with without squareing and if squaring is the only option which i doubt to solve for x can someone show me the proof using these number step by step

thanks

- Algebra -
**Reiny**, Wednesday, May 27, 2009 at 10:13am
you could try graphing.

change to 3√x = x+6

then split it into

y = 3√x and y = x+6

a few points on the graph would be (0,0), (1,3), (4,6) and (9,9)

the second is of course a straight line with slope of 1 and y-intercept of 6

it is immediately obvious that the two graphs cannot intersect, so your equation has no real solution.

The only other option is to square both sides of 3√x = x+6 ,

to obtain the quadratic equation x^2 + 3x + 36 = 0

which only has complex roots as shown by our graph above.

- Algebra -
**Dr Russ**, Wednesday, May 27, 2009 at 10:16am
I am not sure if this helps.

If we rearrange and square each side we end up with

8x^2-12x-36=0

and by inspection we see that one solution is x=3

to find the other divide

8x^2-12x-36 by x-3

which gives

8x-12=0 as the other solution

but check my maths!!

- Algebra -
**Reiny**, Wednesday, May 27, 2009 at 10:23am
if you want a "proof" and development of the quadratic equation, it is obtained by completing the square on

Ax + By + C = 0 as shown in

http://mathworld.wolfram.com/QuadraticEquation.html

(BTW, I notice that DrRuss has a small error in his solution.

when you square 3√x you get 9x not 9x^2)

- Algebra -
**Dr Russ**, Friday, May 29, 2009 at 4:53am
OOOPS That what comes of solving things quickly!!

## Answer this Question

## Related Questions

- math,algebra - can someone help me out factor out this 0=16t^2-122t+180 i have ...
- 8th Grade Algebra - You know how to solve quadratic equations using algebra, ...
- algebra II - I'm quite clueless as to how to solve this. I know the quadratic ...
- Help With Math - Using the quadratic formula to solve equations. -12^2 + 12 x-9...
- Algebra - Hello. I am trying to solve quadratic functions but I'm having ...
- College Algebra - Solve the following equation in the complex number system x^4+...
- Algebra 1 - solve using the addition and multiplication principle 2-2y-5y<65...
- Algebra/Pre-calculus (Quadratic Equations) - A theatre company allows a group of...
- math/science - "calculate the volume of 5g of a substance with a density of 6g/...
- algebra - factor 3a^2(a-b)-6a(a-b)+21(a-b) Can you show me the steps? I'm just ...