quadratic question

[robert mclaughlin]

(x^2)+(7x)=12

i come out with -7+square of 97 over 2

can i break the 97 into 81 and 16

which gives me an answer of
-7+ 9 square 4
over 2


p.s how do i enter latex code, equations would look much better then what im doing

 

[HallsofIvy]

(x^2)+(7x)=12

i come out with -7+square of 97 over 2

You need to say "square root", not "square"! The square root of 4 is 2. The square of 4 is 16.

can i break the 97 into 81 and 16

which gives me an answer of
-7+ 9 square 4
over 2

Are you asking if \(\displaystyle \sqrt{97}= \sqrt{81+ 16}= 9+ 4\)?
Surely you could have checked yourself. 9+ 4= 13. Is the square of 13 (or 13²) equal to 97?

p.s how do i enter latex code, equations would look much better then what im doing

There is a link to a Latex Tutorial at http://mathhelpforum.com/latex-help/266-latex-tutorial.html

 

[JeffM]

(x^2)+(7x)=12

i come out with -7+square of 97 over 2 You mean (I think) the quantity - 7 plus or minus the square root of 97, all over 2.

can i break the 97 into 81 and 16 Yes, but for what purpose?

which gives me an answer of
-7+ 9 square 4 No it does not
over 2


p.s how do i enter latex code, equations would look much better then what im doing

\(\displaystyle x^2 + 7x = 12 \implies x^2 + 7x - 12 = 0 \implies x = \dfrac{- 7 \pm \sqrt{7^2 - 4(1)(-12)}}{2 * 1} = \dfrac{- 7 \pm \sqrt{97}}{2}\)

Now 97 is a prime number, which means that its square root is not an integer. But its square root is obviously between 9 and 10.

\(\displaystyle 9\sqrt{16} = 9 * 4 = 36,\) which is quite a bit bigger than 10.

\(\displaystyle b = 1 \implies a + b \ne a = a * 1 = ab \implies \sqrt{a + b} \ne \sqrt{ab}.\)

\(\displaystyle b \ne 1\ and\ \sqrt{a + b} = \sqrt{ab} \implies a + b = ab \implies ab - a = b \implies a = \dfrac{b}{b - 1}.\)

In other words, what you assumed is a very special case.

Edit: If you know LaTeX, simply put \(\displaystyle \text{\(\displaystyle }\) in front of your code and \(\displaystyle \text{\)}\) behind your code.

 

[robert mclaughlin]

thank you jeff

i was told that 181 could be broken into 2 squares,
100 and 81 and that would break down to 10 and 9
so i ventured that 97 could be 81 and 16--(9, 4) and down to(3,2)

didnt know if it would work, but had to try

thanx

 

[HallsofIvy]

i was told that 181 could be broken into 2 squares,
100 and 81 and that would break down to 10 and 9
so i ventured that 97 could be 81 and 16--(9, 4) and down to(3,2)

didnt know if it would work, but had to try

thanx

Yes, 181 is equal to 100+ 81. Yes, \(\displaystyle \sqrt{100}= 10\) and \(\displaystyle \sqrt{81}= 9\). Then what? Are you saying that \(\displaystyle \sqrt{100+ 81}= 10+ 9\)? What is \(\displaystyle 19^2\)? Is it 181? You can do that, can't you?

 

[JeffM]

i was told that 181 could be broken into 2 squares,
100 and 81 and that would break down to 10 and 9
so i ventured that 97 could be 81 and 16--(9, 4) and down to(3,2)

didnt know if it would work, but had to try

thanx

Have you seen the ad about the woman who said that she had heard on the internet that lies are impossible on the internet. Then her on-line date, a "French model," shows up, scruffy beyond what even the very tolerant French would tolerate and "saying bawn djur." When someone tells you something, test it.

 

[Bob Brown MSEE]

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