## ibew 2 years ago to avoid a negative square root, how can i use the square root property on this ? (x+81)^2 = -158 or am i missing something about the rules of negative numbers and square roots ? I thought negative square roots were not allowed. thanks :)

1. tkhunny

If we allow only Real Numbers, we stop in our tracks and say, "No Solution".

2. godorovg

in math if it is a negative number we call it the number I because it is imaginary which is why we write something like this sqrt -158i if not allowed than no solution..

3. wio

Negative numbers result in imaginary numbers. Imaginary numbers scare me.

4. godorovg

it is nothing to be scared of

5. ibew

the answer to the original equation (generated at math.com) is x= 11 and x=7. the original equation is : x^2 -18x +77 =0 my attempt at the quadratic formula produced : x=(18 ± 2√(61) / 2) i decided i had done something incorrectly and started completing the square from the original equation. can adding 158 to both sides be done while completing the square ? what happened to the reply about adding 158 ?

6. godorovg

okay I know what is wrong

7. godorovg

have you tried this A^2+B^2+C^2 this is the other form of qurad.

8. godorovg

it should be =C^2 not plus srry..

9. ibew

trying it now.

10. godorovg

11. ibew

1585=5929 i thought that formula looked familiar, so i searched for it and found he "Pythagorean theorem" http://en.wikipedia.org/wiki/Pythagorean_theorem perhaps, i have misunderstood something.

12. godorovg

@gemstonegirl come and see this

13. godorovg

need to know something does the problem state that no negative numbers can be the answer?

14. ibew

ok, before the beginning of march, most of algebra was unknown to me. i only had the basic concept of replacing numbers with variables and solving for unknowns. this was required for calculations in ohms law when i was in collage. P=I*E for example. there was nothing complected about it , yet i struggled due to my lack of mathematical knowledge. i used an advanced TI calculator to solve what i did not comprehend. i dropped out of collage (foolish) because it all seemed overwhelming and i moved out of state with a girl that turned out to be insane. that was 5~ ago. when i came back , i found collage debt and a new opportunity with an apprenticeship program by IBEW (international brotherhood of electrical workers). there is an aptitude test near the end of April that involves algebra. i have been cramming my head with algebra ever since the day i learned of this. so, do not fret over your lack of algebra knowledge or mistakes, because i have less ten two months of algebra study ;)

15. godorovg

16. godorovg

@ibew I amm studing math myself and this Summer I start on-line at IU East so math is my life and mistakes like this I should not make..

17. godorovg

@ibew there is no answer for this problem. also use the sqrt to see there is no answer to this problem ...

18. ibew

is that allowed while "completing the square" ?

19. ibew

the original equation is : x^2 -18x +77 =0

20. ibew

i did: "ibew Medals 0 the answer to the original equation (generated at math.com) is x= 11 and x=7. the original equation is : x^2 -18x +77 =0 my attempt at the quadratic formula produced : x=(18 ± 2√(61) / 2) i decided i had done something incorrectly and started completing the square from the original equation. can adding 158 to both sides be done while completing the square ? what happened to the reply about adding 158 ? an hour ago" "

21. ibew

:)

22. godorovg

23. ibew

this web site says there is an answer. http://www.algebrahelp.com/calculators/equation/calc.do;jsessionid=52F7E4DBE8C8F1538B2EE5187783E04C?equation=x^2+-18x+%2B77+%3D0+&solvf=AUTO i am looking it over now. i also added your link to my "math" book marks folder, thanks :)

24. godorovg

25. ibew

it does not use the quadratic formula or "completing the square" . i am nor well versed on factoring polynomials . i have memorizing the quadratic formula and completing the square because they achieve results 100% of the various problems.

26. ibew

if any one can show me what i am doing wrong or how to get beyond this "soon to be" negative square root", it would be greatly appreciated. :)

27. ibew

if any one has successfully solved the equation with the quadratic formula, that would help also.

28. gemstonegirl

i think the decision is unanimous that there is no solution to this :D ure online answers may have been wrong ...never know

29. ibew

@Luis_Rivera , thanks, i will post the question again with more information.

30. gemstonegirl

lol sorry i dont know that far ..but u will have to change up the equation ...