Solve equation sq root(1+3x)=x-1?



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Posted on (Answer #2)

Solve `sqrt(1+3x)=x-1` :

`sqrt(1+3x)=x-1`  Square both sides:

** Be aware that squaring can create extraneous solutions -- solutions that follow algebraically but do not work in the original equation **





x=0 or x=5

Check for extraneous solutions:

If x=0 then `sqrt(1+3(0))=(0)-1 ==> 1=-1` which is not true so x=0 is extraneous.

If x=5 then `sqrt(1+3(5))=(5)-1 ==> 4=4`


The solution is x=5


The graphs of the left side and right side -- the solution(s) is/are the points of intersection:

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embizze's profile pic

Posted on (Reply #1)

This is incorrect. x=0 is extraneous. You have found the intersections of the line y=x-1 and the parabola `x=1/3(y^2-1)` ; however we are given the function representing the upper half of the parabola only.

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