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4. Solve `t`
`2 + 20t +1/2(-9.8)t^2 =5`
`t = (-b ± sqrt(b^2-4ac))/(2a)`
`=> t_1 = 0.16, t_2 = 3.9`
1) Simplify equation:
`=> -3 + 20t -4.9t^2 =0`
2) Use quadratic formula: `t = (-b ± sqrt(b^2-4ac))/(2a)`
where
`a = -4.9`
`b =20 `
`c =-3`
`=> t = (-20 ± sqrt((-20)^2-4(-4.9)(-3)))/(2(-4.9))`
`=> t = (-20±18.47)/-9.8`
`=> t_1 = 0.16, t_2 = 3.9`
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