How do you solve #sqrt[x+5]=3x-7# and find any extraneous solutions?
Simplifying the equation would involve first getting rid of the square root:
Simplifying further, we can expand out the square on the right side of the equation:
Since this is a quadratic equation, we want to put everything on one side and then find the zeros of the expression:
Using the quadratic formula (since we cannot factor the expression),
Using a calculator to find the value of this expression,
Plugging the first value back into the equation, we get a valid equation:
However, when we plug the second value back into the equation, we have this:
Since the right side is negative, the second value that we got for
all values of
For the solution to remain within the set of numbers called Real the square root must be of a value that is not negative.
Thus all values of
Square both sides
To comply with convention write as:
In this case:
However, as per smartspot2, substituting 1.485 back into the original question proves this value to fail if you use the 'Principle Square Root'. Thus by his approach there is only 1 value that is correct: