# Irrasjonale likninger (don't know what it is in English)

• August 31st, 2005, 01:30 AM
Trond
Irrasjonale likninger (don't know what it is in English)
Example:

x = √3x+7-1

x+1 = √3x+7

(x+1)² = (√3x+7)²

x²+2x+1 = 3x+7

Question: Why +2x

x²-6-x = 0

Question: Why -6-x?

x = -2 OR x = 3

Question: How can you see the answer will be -2 or 3?
• August 31st, 2005, 03:04 PM
sara8
to expand the squared bracket like your example (x+1)^2 you square the x and then the number(1) then you multiply 1 by x by 2 (the power above the square) about your second question you move the l.h.s to the R.H.S with an opposite sign it will be x^2 +2x+1-3x-7=0 this is to be put in the form of the quadratic equation then you the equation becomes x^2-6x-1=0 this is to be able to find the roots of the quadrtic equation by the quadratic formula or by factorizing .I hope this helps .

Sara,
• September 6th, 2005, 05:08 PM
Trond
Now I understand why I couldn't figure it out. I'm taking math and had forgotten all about it, so I'm starting from scratch. It's been many years. Thanks for reply though.