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OCR Completing the square help!

I've always struggled with completing the square and questions when a is not 1 is so confusing! Like for example this question. Apparently the answers 1.46 or -0.46.
question: 3x^2-3x=2
my answer:
3x^2-3x-2=0
divide by 3
x^2-x-2/3=0
(x-0.5)^2
(x-0.5)(x-0.5)
x^2-x+5/12 i got 5/12 from 2/3-1/4
(x-0.5)^2= +or-5/12
x=+or-√5/12 +0.5 (the 0.5 is not √)
x=1.14 or -0.14

please help :frown: the actual answer is 1.46 or -0.46
Reply 1
Avatar for Notnek
Notnek
21
You are saying that

x2−x−23=(x−0.5)2+23−14\displaystyle x^2-x-\frac{2}{3} = (x-0.5)^2 +\frac{2}{3}-\frac{1}{4}

But this is not correct. Notice the 23\frac{2}{3} is negative on the left-hand-side so it should be negative on the right-hand-side.


(In future, you should post maths help questions in the "Maths" forum, not the "Maths Exams" subforum.)
(edited 11 years ago)
Reply 2
Avatar for Prada16
Prada16
OP
ok thanks i posted here coz i didnt see the 'create thread' in the maths forum so posted here instead...ive found it now though :smile:

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