Find an equation in slope-intercept form of the line that has slope -3 and passes through point a(9,4)

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Mrs. avila is buying a wallpaper border to go on all of her kitchen walls. she wants to buy 5 extra feet of wallpaper border than she needs to be sure she has enough. she buys 55.5 feet of the border. the store owner selling the border uses the width of mrs. avila's kitchen to determine that the length of her kitchen must be 14.5 feet.

Find the condition that the zeros of the polynomial f(x) = x^3+3px^2+3px+r may be in a. p.