SOLUTION: how is the following equation solved z - 7z1/2 + 12 = 0

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Question 261529: how is the following equation solved
z - 7z1/2 + 12 = 0

Answer by jsmallt9(3758) About Me  (Show Source):
You can put this solution on YOUR website!
z+-+7z%5E%281%2F2%29+%2B+12+=+0
The key to solving this equation is to recognize that z+=+%28z%5E%281%2F2%29%29%5E2. This is what makes this a quadratic equation. If you have trouble seeing this, then we can use a temporary variable:
Let q+=+z%5E%281%2F2%29
then q%5E2+=+z
Replacing z and sqrt%28z%29 with q%5E2 and q respectively your equation becomes:
q%5E2+-7q+%2B+12+=+0
This is clearly a quadratic equation. We can solve this by factoring:
%28q-3%29%28q-4%29+=+0
From the Zero Product Property we know that this product can be zero only if one of the factors is zero. So:
q-3+=+0 or q-4+=+0
Solving these we get:
q+=+3 or q+=+4

Of course we are not interested in what q is. We want a solution for z. So at this point we replace q with sqrt%28z%29:
z%5E%281%2F2%29+=+3 or z%5E%281%2F2%29+=+4
We now have one more step. We need to square both sides of these equations giving us:
z+=+9 or z+=+16

Using a temporary variable is not required. But they can be helpful until you get used to working without them. Here is a solution which does not use a temporary variable:
z+-+7z%5E%281%2F2%29+%2B+12+=+0
Factor:
%28z%5E%281%2F2%29+-+3%29%28z%5E%281%2F2%29+-+4%29+=+0
Zero Product Property:
z%5E%281%2F2%29+-+3+=+0 or z%5E%281%2F2%29+-+4+=+0
Solve:
z%5E%281%2F2%29+=+3 or z%5E%281%2F2%29+=+4
z+=+9 or z+=+16