# Thread: Solving an algerbraic equation.

1. ## Solving an algerbraic equation.

Hi all.
I got this question from my example booklet, which has the question worked. However, im not quite sure how the problem is solved, and i cant follow how the exmaple booklet does it.

If someone could break down the steps for me that would be amazing.

This is what the booklets steps are:

-300 = 0 + (1/2) * (-9.8) * t^2

t^2 = -300 * 2 / -9.8

t^2=61.22

hence, t = 7.8s

I dont understand how it goes from the first line to the second one.

Any help would be greatly appreciated.
Thanks.

Hi all.
I got this question from my example booklet, which has the question worked. However, im not quite sure how the problem is solved, and i cant follow how the exmaple booklet does it.

If someone could break down the steps for me that would be amazing.

This is what the booklets steps are:

-300 = 0 + (1/2) * (-9.8) * t^2

t^2 = -300 * 2 / -9.8

t^2=61.22

hence, t = 7.8s

I dont understand how it goes from the first line to the second one.

Any help would be greatly appreciated.
Thanks.
$\displaystyle -300=0+\frac{1}{2}(-9.8)t^2$ step 1 simplify this gives

$\displaystyle -300=\frac{-9.8}{2}t^2$ Isolate the variable by multiplying both sides of the equation by the reciprocal of the fraction

$\displaystyle -300\left(\frac{2}{-9.8}\right)=\left( \frac{2}{-9.8}\right)\frac{-9.8}{2}t^2$ Simplify both sides

$\displaystyle \frac{600}{9.8}=t^2$ Now take the square root of both sdies

$\displaystyle \sqrt{\frac{600}{9.8}}=\sqrt{t^2} \implies \sqrt{\frac{600}{9.8}}=t$

Now just put the last bit into a calculator

$\displaystyle t=\sqrt{\frac{600}{9.8}} \approx \sqrt{61.2244} \approx 7.82$

3. Thank you so much

-300 = 0 + (1/2) * (-9.8) * t^2

t^2 = -300 * 2 / -9.8

t^2=61.22

hence, t = 7.8s

Well, that's sure a confusing way to solve something simple;
why not do the multiplication FIRST:
-300 = -4.9 t^2 ; then:
t^2 = 300 / 4.9
t = SQRT(300 / 4.9)

5. Originally Posted by Wilmer
Well, that's sure a confusing way to solve something simple;
why not do the multiplication FIRST:
-300 = -4.9 t^2 ; then:
t^2 = 300 / 4.9
t = SQRT(300 / 4.9)

How did you get the positive 4.9? I can only manage to get a postive 300 and a negative 4.9 before the square root...

6. $\frac{-300}{-4.9}= \frac{300}{4.9}$. How did you get the numerator positive and the denominator negative?

7. Ahahaha dont ask... i may or may not have dont the equation completely wrong. I understand the first solution, but not the second one posted.

8. You don't understand that:
-300 = -4.9 t^2
t^2 = -300 / -4.9
t^2 = 300 / 4.9
??