Thread: Equation with radical

here's another i can't solve.

t - 5√t - 14 = 0

i added 14 to both sides and then squared them. then i minused 196 and am left with t^2 + 15t -196 = 0

this doesn't work, what have i done wrong?

Originally Posted by Miasmagasma

here's another i can't solve.

t - 5√t - 14 = 0

i added 14 to both sides and then squared them. then i minused 196 and am left with t^2 + 15t -196 = 0

this doesn't work, what have i done wrong?

Originally Posted by skeeter

cheers but why did my method not work?

Originally Posted by Miasmagasma

cheers but why did my method not work?

Because . If you post all your working on how you got that (wrong) result your error(s) can be explained.

Originally Posted by mr fantastic

Because . If you post all your working on how you got that (wrong) result your error(s) can be explained.

well i thought t times 5√t = 5t which is no doubt wrong. how do you work that out?

Originally Posted by Miasmagasma

here's another i can't solve.

t - 5√t - 14 = 0

i added 14 to both sides and then squared them. then i minused 196 and am left with t^2 + 15t -196 = 0

this doesn't work, what have i done wrong?

Notice it looks very much like a quadratic.

So use a dummy variable .

This would mean .


Your equation becomes





or .


Note that, since , the solution is unusable.


This means, since , that .

Originally Posted by Miasmagasma

well i thought t times 5√t = 5t which is no doubt wrong. how do you work that out?

How can ? If t = 4 do you get a correct result from this? And what then do you think is equal to?

As you surmised, . On the other hand, .