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Mathematics 9 Online
iosangel:

3^2x=81^x+9

iosangel:

Do i use a different rule other than power rule to solve the other side?

snowflake0531:

\[3^{2x} = 81^x+9\] can you first make all the bases 3?

snowflake0531:

wait there would be no solution do you mean 81^{x+9)?

snowflake0531:

\[3^{2x}=81^{x+9}\\3^{2x}=3^{(4)({x+9})}\]

snowflake0531:

you probably know how to solve it from there

iosangel:

Sorry, i didnt see you reply, but how did you get that? what rule did you use?

snowflake0531:

\[3^{2x}=81^{x+9}\\3^2x = 3^4 to ~the~power~of~x+9\\3^{2x}=3^{(4)({x+9})}\]

snowflake0531:

a^b^c=a^(bc)

iosangel:

ok so first 3^2x=81^x+9 =3^2x=3^4<


you got this because 3^4=81?

snowflake0531:

3^2x does not equal 3^4

iosangel:

would that be a base rule or exponent rule?

iosangel:

i meant 3^4=81

snowflake0531:

it would be the power rule... base rule is for logarithms.. exponent rule is for something else

iosangel:

sorry, thats confusing

snowflake0531:

81^x+9 is 3^4 ^ x+9 so by the power rule it equals 3^(4(x+9))

iosangel:

but you changed bases,?

snowflake0531:

yeah latex doesn't allow me to do double exponents i think

snowflake0531:

1 attachment
snowflake0531:

i don't think the names of rules really matter

snowflake0531:

it's what to actually do

iosangel:

yes

iosangel:

but i alwyas forget that rule

iosangel:

thank you thats the rule i was looking for

snowflake0531:

yeah I guess it's called power rule for exponents

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