SOLUTION: Hi! I always like to try to figure these out before I ask for help, so can you tell me if I am anwhere where I need to be on this one? Thanks!!! Solve using the square root pr

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: Hi! I always like to try to figure these out before I ask for help, so can you tell me if I am anwhere where I need to be on this one? Thanks!!! Solve using the square root pr      Log On


   

Question 81517: Hi! I always like to try to figure these out before I ask for help, so can you tell me if I am anwhere where I need to be on this one? Thanks!!!
Solve using the square root property:
2x2 – 3 = 15
2x^2=15
x=√15 or x=-√15
x=√3√5 or x=-√3√5
Found 2 solutions by mathdoc316, Earlsdon:
Answer by mathdoc316(9) About Me  (Show Source):
You can put this solution on YOUR website!

well it looks sort of like the right steps,
but your algebra is losing terms and factors all over the place
I guess you have a confusion about what is done to balance an equation.
Imagine a see-saw.
On each end of the see-saw is a twin. Art and Bart. They both weigh 42 pounds. A = B
Then you can add a 5 pound weight on each end
A + 5 = B + 5
Now there is 47 pounds on each end
Now you make one of the 5 disappear
A + 5 > B
47 > 42
Please notice carefully here that the equation is not balanced any more.
Now it has become an inequality.
47 and 42 are not the same number.
One twin will now go up into the air and the other one will land on his butt.
This is not a very nice joke to do! But kind of funny to watch!
What you need is:
2x%5E2+-+3+=+15
Add 3 to each side. The same thing is done to each side, so the equation stays balanced!
2x%5E2+-3+%2B+3+=+15+%2B+3
2x%5E2+=+18
Now you divide BOTH sides by 2 to isolate the x^2 and keep the equation balanced
x%5E2+=+18%2F2+=+9
Now the square root can be used
x+=+%2B3 or x+=+-3
I am not sure what "the square root principle" is. I have heard +3 called "the principal square root" of 9 and then -3 is the other square root of 9 that is not the principal one. People often write "principle" when they really mean "principal", even in prestigious publications such as the Georgia Tech alumni magazine, or in their own job titles, but I hope you will be able to work it out. Principal is a noun or an adjective, and Principle is always a noun I think.





Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Solve for x:
2x%5E2-3+=+15 Add 3 to both sides.
2x%5E2+=+18 Divide both sides by 2.
x%5E2+=+9 Take the square root of both sides.
x+=+3 or x+=+-3