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How do you solving the solution of each system using elimination?

Aprojectile is thrown upward so that its distance above the ground after t seconds is given by the function h(t) = -16t2 + 704t. after how many seconds does the projectile take to reach its maximum height?

The coordinates of vortex a’ are (8,4) (-4,2) (4,-,4) the coordinates of vortex b’ are (6,6)(12,-,12)(12,12) the coordinates of vortex c’ are(-2,,12)(4,12)(12,-4)