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# quadratic formulas: x squared minus 1= 2x

x2-1=2x

### 2 Answers by Expert Tutors

Philip P. | Effective and Affordable Math TutorEffective and Affordable Math Tutor
5.0 5.0 (428 lesson ratings) (428)
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x2 - 1 = 2x

First, put the equation into standard form (ax2+bx+c=0):

x2 - 2x -1 = 0

This equation does not factor readily, so let's use the Quadratic Formula:

x = (-b/2a) ± (1/2a)(b2 - 4ac)1/2

For your problem, a=1, b=-2, and c=-1:

x = (2/2) ± (1/2)[(-2)2 - 4(1)(-1)]1/2

x = 1 ± (1/2)[4 + 4]1/2

x = 1 ± (1/2)(√8) = 1 ± (1/2)(2√2)

x = 1+√2 and 1-√2

same answer, sorry I repeated the problem Philip.
Francisco E. | Francisco; Civil Engineering, Math., Science, Spanish, Computers.Francisco; Civil Engineering, Math., Sci...
5.0 5.0 (1 lesson ratings) (1)
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x2 - 1 = 2x; reorganizing the equation we obtain: X^2 - 2x -1
Quadratic solution: (-b ± √(b^2- 4ac))/2a
Then, plugging into the formula we have:
(2 ± √(4+(4*1*1))/2
x1 = (2 + √8)/2 = 2.41421
x2 = (2 - √8)/2 = 0.41421
CHECK!!!!!!!!!!!!!!!!!!!!!!!