Melody

Which sum and difference formulas?

This is a calculator site!  Do it yourself.

I'll give you a different example and then you can do your own one.

(2,7)

y<12

y<8-x

ok

x=2 and y=7  is this in the region

is   y<12 .... well  7<12  so that is true

is   y<8-x ..... umm   is 7<8-2  ....    is 7<6 ?     NO it is not.

SO (2,7) is NOT a part of the region.

(2,7) is NOT a solution to the system of equations :)

I do not ever remember seeing a question like this before :)

ratio of 5 to 4 with product of 81

Let the numbers be   (5x/9) and  (4x/9)

This has nothing to do with the 81.  The nine comes from   4+5=9

\(\frac{5x}{9}\times \frac{4x}{9}=81\\ \frac{20x^2}{81}=81\\ 20x^2=81^2\\ 20x^2=6561\\ x^2=328.05\\ x=\sqrt{32805}\div10\)

factor(32805) = 3^8*5

\(x=\frac{\sqrt{81*81*5}}{10}\\ x=\frac{81\sqrt{5}}{10}\\\)

so the numbers are 

\(\frac{5}{9}\;of\; 8.1\sqrt5 \quad and \qquad \frac{4}{9}\;of\; 8.1\sqrt5\\ \quad4.5\sqrt5 \qquad and \qquad 3.6\sqrt5\\\)

check

4.5*sqrt(5)*3.6*sqrt(5) = 81

and

4.5*sqrt(5)/(3.6*sqrt(5)) = 1.25 = 5/4

*

Term is the name of a maths term   

or with an   [x^y]    box   :)

2³ = 8

2  [x^y] 3 = 8

2 ^ 3 = 8

It is 0+3 = 3

For those who may be interested, this is Max's question I am referring to

I did look at your calculus question Max but I'd have to look stuff up before I could have a hope of answering it.

It seemed like a lot of effort.  Having said that, it doesn't look like it should be that hard.  :/

It doesn't even look like calculus but that is probably just me displaying my total ignorance.....

Isn't there some simple formula you can use?

Actually Max that was YOUR fault.

I copied and pasted the first line of your LaTex coding, that's how come I missed the -4 !

You might be the self proclaimed 'Smartest Cookie in the World" but you cannot claim to be the most careful one!  :))