C Carolyn P New member Jul 9, 2009 #1 If 3x^2-2x+7=0, then (x-1/3)^2 = Help, I'd would be giant help if you could go through this step by step. The answer is supposed to be -20/9, I just don't get how it gets there.
If 3x^2-2x+7=0, then (x-1/3)^2 = Help, I'd would be giant help if you could go through this step by step. The answer is supposed to be -20/9, I just don't get how it gets there.
W wt rd Guest Jul 9, 2009 #2 Let start by: (x - 1/3)^2 = x^2 - 2x/3 + 1/9 = 3x^2/3 - 2x/3 + 1/9.... (common denominator is 3) = (1/3)(3x^2 - 2x) + 1/9 .... (try to get the first group close to the given info) = (1/3)(3x^2 - 2x + 7 - 7) + 1/9 ..... (since + 7 - 7 = 0) = 1/3)(3x^2 - 2x + 7) - (1/3)*7 + 1/9 = (1/3) * ( 0 ) - 7/3 + 1/9 (since the given 3x^2-2x+7=0) = - 7/3 + 1/9 = -(21 + 1)/9 ....(common denominator is 9) = - 20/9; is the answer. The work done here is try to figure out the (x - 1/3)^2 along with the given information, then subtitute. Good Luck!
Let start by: (x - 1/3)^2 = x^2 - 2x/3 + 1/9 = 3x^2/3 - 2x/3 + 1/9.... (common denominator is 3) = (1/3)(3x^2 - 2x) + 1/9 .... (try to get the first group close to the given info) = (1/3)(3x^2 - 2x + 7 - 7) + 1/9 ..... (since + 7 - 7 = 0) = 1/3)(3x^2 - 2x + 7) - (1/3)*7 + 1/9 = (1/3) * ( 0 ) - 7/3 + 1/9 (since the given 3x^2-2x+7=0) = - 7/3 + 1/9 = -(21 + 1)/9 ....(common denominator is 9) = - 20/9; is the answer. The work done here is try to figure out the (x - 1/3)^2 along with the given information, then subtitute. Good Luck!
J John F New member Jul 9, 2009 #3 (x - 1/3)^2 = x² - 2/3 x + 1/9 = 1/3 (3x² - 2x + 1/3) As 3x² - 2x + 7 = 0, you get : 3x² - 2x + 1/3 = 3x² - 2x + (21/3 - 20/3) = (3x² - 2x + 7) - 20/3 = - 20/3 => 1/3 (3x² - 2x + 7 - 20/3) = (x - 1/3)² = - 20 <=== answer *******
(x - 1/3)^2 = x² - 2/3 x + 1/9 = 1/3 (3x² - 2x + 1/3) As 3x² - 2x + 7 = 0, you get : 3x² - 2x + 1/3 = 3x² - 2x + (21/3 - 20/3) = (3x² - 2x + 7) - 20/3 = - 20/3 => 1/3 (3x² - 2x + 7 - 20/3) = (x - 1/3)² = - 20 <=== answer *******
