The height s metres of a mass thrown vertically upward at a time t seconds given by

S=40t-13t2

Show when 25m= 40t - 13t2, 13t2 - 40t + 25 = 0

There is something about what you do to one side you have to do to the other?

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- Mar 20th 2012, 02:42 AMHollieMay2600Maths Homework.
The height s metres of a mass thrown vertically upward at a time t seconds given by

S=40t-13t2

Show when 25m= 40t - 13t2, 13t2 - 40t + 25 = 0

There is something about what you do to one side you have to do to the other? - Mar 20th 2012, 02:49 AMProve ItRe: Maths Homework.
What is m?

- Mar 20th 2012, 03:02 AMHollieMay2600Re: Maths Homework.
- Mar 20th 2012, 03:31 AMprincepsRe: Maths Homework.
- Mar 20th 2012, 05:49 AMHallsofIvyRe: Maths Homework.
No. This should be $\displaystyle 13t^2- 40t+ 25= 0$ which has, by the quadratic formula, solutions

$\displaystyle \frac{40\pm\sqrt{1600+ 1300}}{26}= \frac{40\pm\sqrt{2900}}{26}$.

Quote:

(1)+(2) : $\displaystyle -26t_2=0 \Rightarrow t_2=0$

hence :

$\displaystyle 40t=25 \Rightarrow t=\frac{5}{8}$

- Mar 20th 2012, 05:56 AMprincepsRe: Maths Homework.
Yes it is clear now , after original post is edited .