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What is best way to getting answer for my exam is

Find the center and the radius of the circle with the equation: x^2-2x+y^2+4y+1=0?

Astudent must have an average on five test that is greater than it equal to 80% but less than 90% to receive a final grade of b. devon's greades on the first four test were 78% 62% 91% and 80% what range if grades on the fifth test would give him a b in the course? ( assuming the highest grade is 100%)