what am i doing wrong? 2n - 3(4n + 5) = -6(n - 3) - 1  TOPIC_SOLVED

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what am i doing wrong? 2n - 3(4n + 5) = -6(n - 3) - 1

Postby infinite_product on Thu Sep 29, 2011 9:22 pm

okay, i am an eighth grader taking algebra 1 and so far its been a breeze. but now we're solving equations with variables on both ends and i am sorta lost. i say sorta because i get it and understand what to do (combine like terms, opposite operations, ...the works...) but then i get to solving the problem and i do everything how the book and my teacher says, but the answers just don't end up working out when i plug my answers in for the variables...

heres one of my problems:

what is the solution of 2n - 3(4n + 5) = -6(n - 3) - 1 ?

i did this:

distributed, so i rewrote the problem as: 2n - 12n + 15 = -6n - -18 - 1
then i combined like terms: 2n + -12n + 6n = -15 + 18 + -1 and got: -4n = 2
then i divide each side by -4 to isolate the variable and 2 / -4 is - 1/2


according to my teacher, the answer is -8. no matter how many times i rework this problem, i still get negative one half..... :roll:

can someone please tell me what i am doing wrong here? :confused:
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Postby stapel_eliz on Thu Sep 29, 2011 9:31 pm

infinite_product wrote:what is the solution of 2n - 3(4n + 5) = -6(n - 3) - 1 ?

i did this:

distributed, so i rewrote the problem as: 2n - 12n + 15 = -6n - -18 - 1

How are you getting that -3(+5) equals +15 instead of -15? :wink:

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Re: what am i doing wrong? 2n - 3(4n + 5) = -6(n - 3) - 1

Postby infinite_product on Fri Sep 30, 2011 12:10 am

hmm... i think i was thinking negative three.......... :lol: thanks.....
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