
Susanne R. answered 04/16/15
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Y^2-4y-5=0. First add 5 to both sides of the equation, y^2-4y = 5. Then complete the square by dividing the term in front of y (4) by 2 and then squaring it, so you get y^2-4y+4 = 5 + 4. So the answer is (y-2)^2 = 9. So now you can solve for y, by taking the square root of both sides of the equation, so you get y-2 = +3. There are 2 answers. y = 2 + 3, or 5 and y =2-3, or -1.