1. Solve to find the zeros of y = -0.8x 2 + 84 Replace y = 0 Eliminate the constant c by undoing + 84 Divide by the coefficient A on both sides. Undo -0.8 Eliminate the squaring by taking the square root of both sides. Remember that there are always two answers when taking the square root. 0 = -0.8x 2 + 84 -84 = -0.8x 2 105 = x 2 10.2 and -10.2 = x

2. So the zeros of the function are located at: (10.2, 0) and (-10.2, 0)

3. Solve to find the zeros of y = -x 2 + 35 Replace y = 0 Eliminate the constant c by undoing + 35 Divide by the coefficient A on both sides. Undo -1 Eliminate the squaring by taking the square root of both sides. Remember that there are always two answers when taking the square root. 0 = -x 2 + 35 -35 = -x 2 35 = x 2 5.9 and -5.9 = x

4. So the zeros of the function are located at: (5.9, 0) and (-5.9, 0)

5. Summary to solve by the square root method:  Only can be used for functions in the form: y = ax 2 + c  Set the function equal to zero  Undo the constant c on both sides  Divide by the coefficient a on both sides  Take the square root of both sides; remembering that there are two possible answers; a positive and a negative.