What is the missing reason for the following proof?

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The graph shows the distance y, in inches, a pendulum moves to the right (positive displacement) and to the left (negative displacement), for a given number of seconds x. how many seconds are required for the pendulum to move from its resting position and return? enter your answer in the box.

Solve each quadratic equation by factoring and using the zero product property. x^2 - 8x + 30 = 3x

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