SOLUTION: Mark uses a slingshot to shoot a marble straight upwards with an initial velocity of 56 feet per second. Under these circumstances, the height of the marble is given by the formula

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Mark uses a slingshot to shoot a marble straight upwards with an initial velocity of 56 feet per second. Under these circumstances, the height of the marble is given by the formula      Log On


   

Question 301482: Mark uses a slingshot to shoot a marble straight upwards with an initial velocity of 56 feet per second. Under these circumstances, the height of the marble is given by the formula +h=56t+-+16t%5E2+ where h is the height, in feet, after t seconds. How long does it take for the marble to reach a height of 40 feet?
Use a polynomial Equation to solve this problem
It would also be helpful for me to understand if you included the initial equation in the reply. Thanks!
Answer by checkley77(12844) About Me  (Show Source):
You can put this solution on YOUR website!
h=56t-16t^2
40=56T-16T^2
16T^2-56T+40=0
8(2T^2-7T-5)=0
T+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
T=(7+-SQRT[-7^2[-7^2-4*2*-5])/2*2
T=(7+-SQRT[49+40])/4
T=(7+-SQRT89)/4
T=(7+-9.434)/4
T=(7+9.434)/4
T=16.9434/4
T=4.11 ANS.
T=(7-9.434)/4
T=-2.434/4
T=-.61 ANS.