1. Because if the value of "a" is 0 then the equation will not be a quadratic equation. One of the conditions in having a quadratic equation by not having 0 as your "a".
2. a. square root method
in this type of equation, the square method is the most appropriate method to use because 36 is a perfect square. moreover, the first term and the constant are the only ones given.
Hope It Helps
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