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Mathematics 22 Online
OpenStudy (anonymous):

Question in comments, please help.

OpenStudy (anonymous):

If a^m * a^n = a^mn then find the value of m(n-2) + n(m-2).

OpenStudy (auctoratrox):

a^m * a^n should equal a^(m+n), not a^mn

OpenStudy (anonymous):

I know, if it was a^(m+n), then it is one of the laws of exponents and all values of m and n will satisfy the condition. They are asking two numbers m and n where m+n=mn

OpenStudy (experimentx):

\[ a^{(m+n - mn)} = a^0 \] Squaring both sides, \[ a^{2(m+n) - 2mn} = a^{2*0} = a^0 \] Rest is easy!!

OpenStudy (anonymous):

So, 2(m+n) - 2mn = 0 Am I right?

OpenStudy (experimentx):

\[ m(n - 2) + n(m-2) = mn - 2m + mn - 2n = 2mn - 2(m+n) \]

OpenStudy (experimentx):

I think so..

OpenStudy (anonymous):

But there are two variables ... don't you think trial ad error would be easier?

OpenStudy (anonymous):

*trial and error.

OpenStudy (anonymous):

Please help @experimentX

OpenStudy (auctoratrox):

you know that m + n = mn right? so do the distributive property on the original question and substitute back in with m + n = mn.

OpenStudy (auctoratrox):

if we do the distributive property we end up with mn - 2m + nm -2n, now just put in m + n wherever you see mn. and you get zero.

OpenStudy (anonymous):

You mean: m+n-2m+m+n-2n = 2m+2n-2m-2n = 0 Thanks a lot!!

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