Water is added to two containers for 16 minutes. The equations below model the ounces of water, y, in each container after x minutes. At the time after the start when the containers hold the same amount of water, how much water do they hold?

Container A: y=16x+104
Container b: y=-2x^2+40x+160

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1 answer

To find when the containers hold the same amount of water, we need to set the two equations equal to each other and solve for x:

16x + 104 = -2x^2 + 40x + 160

Rearranging to put the equation in standard form:

2x^2 + 24x + 56 = 0

Dividing the equation by 2 to simplify:

x^2 + 12x + 28 = 0

Factoring the quadratic equation:

(x + 2)(x + 14) = 0

Setting each factor equal to zero:

x + 2 = 0
x = -2

x + 14 = 0
x = -14

Since the time after the start cannot be negative, we discard the negative solution x = -14. Therefore, the containers hold the same amount of water at x = -2 minutes, which means they have the same amount of water when they are both filled initially.

Substitute x = -2 back into either equation to find how much water they hold:

Container A: y = 16(-2) + 104 = 72 ounces
Container B: y = -2(-2)^2 + 40(-2) + 160 = 72 ounces

Therefore, both containers hold 72 ounces of water when they have the same amount.