Ann.without.an.e Posted March 26, 2013 Share Posted March 26, 2013 Problem is this.... Assume ^2 is to the power of 2 since I can't find a symbol for it F(x) = x^2+2x+2 find f(m-1) I get this (I will show my work :) f(m-1) = (m-1)^2 + 2(m-1) + 2 m^2+1+2m-2+2 m^2+2m+1 My key says the answer should be m^2+1 Is it incorrect or did I go wrong somewhere? Granted, I am NOT an algebra gal so I could most definitely be incorrect, lol. Thanks ya'll Quote Link to comment Share on other sites More sharing options...
Dana Posted March 26, 2013 Share Posted March 26, 2013 Problem is this.... Assume ^2 is to the power of 2 since I can't find a symbol for it F(x) = x^2+2x+2 find f(m-1) I get this (I will show my work :) f(m-1) = (m-1)^2 + 2(m-1) + 2 You're correct here. Next line is wrong. Exponents don't distribute over addition or subtraction. You have to use square of difference formula or write out (m-1)(m-1) and distribute. You should get next.... m^2 -2m +1 +2m-2+2 m^2+1 Quote Link to comment Share on other sites More sharing options...
Jann in TX Posted March 26, 2013 Share Posted March 26, 2013 You made a classic mistake when you squared the (m-1) think of it as (m-1)(m-1) and it should be m^2-2m+1 not m^2-1 (you left out midle term!) Quote Link to comment Share on other sites More sharing options...
Matryoshka Posted March 26, 2013 Share Posted March 26, 2013 The answer key is right. Your mistake is trying to distribute the exponent in the first term over subtraction. (m-1)^2 does not equal m^2+1, it is the whole expression squared, which is (m-1)(m-1), which distributes out with FOIL to m^2-2m+1. The other terms your dealt with properly, so that would be (m^2-2m+1) + (2m-2) + 2, which reduces to m^2+1 Quote Link to comment Share on other sites More sharing options...
Ann.without.an.e Posted March 26, 2013 Author Share Posted March 26, 2013 Aha, thank you. I told you that I am NOT a math gal. DD rarely misses an answer on a test so I thought the key was incorrect. When I showed her your post she immediately knew what she did wrong. Thank you so much! Ya'll rock, but you know that already :) Quote Link to comment Share on other sites More sharing options...
kiana Posted March 26, 2013 Share Posted March 26, 2013 This error is so common that it's often called 'The freshman's dream' or 'the freshman's mistake' -- so she's in good company. If she can manage to consistently remember not to do this, she'll be ahead of about 50% of college students. (seriously) Quote Link to comment Share on other sites More sharing options...
EKS Posted March 26, 2013 Share Posted March 26, 2013 Another vote for the answer key. Quote Link to comment Share on other sites More sharing options...
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