document.write( "Question 368989: A tennis ball is rolled down a valley along a slope shaped like a parabola. After t seconds, its height above sea level in meters is modeled by the function h(t)=t^2-8.9t+14. After how many seconds does the ball reach its minimum height? What is that minimum height? Round to the nearest hundredths place and use proper units in your answer. \n" ); document.write( "
Algebra.Com's Answer #262961 by nerdybill(7384)\"\" \"About 
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h(t)=t^2-8.9t+14
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\n" ); document.write( "We know it is a \"quadratic\" because it is in the form of:
\n" ); document.write( "Ax^2 + Bx + C
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\n" ); document.write( "Looking at the coefficient associated with the t^2 term, since it is positive (happy face) the parabola opens upwards. The vertex will give you the minimum.
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\n" ); document.write( "After how many seconds does the ball reach its minimum height?
\n" ); document.write( "t = -b/(2a)
\n" ); document.write( "t = -(-8.9)/(2*1)
\n" ); document.write( "t = (8.9)/2
\n" ); document.write( "t = 4.45 secs
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\n" ); document.write( "What is that minimum height?
\n" ); document.write( "Plug the value above back into:
\n" ); document.write( "h(t)=t^2-8.9t+14
\n" ); document.write( "h(4.45)=4.45^2-8.9(4.45)+14
\n" ); document.write( "h(4.45)= -5.80 meters
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