Year 12s: what will be the first way you research your future options? >>

easiest method to solve this

t(3t^4-4t^2-15)=0

Easiest method to solve this?

Thanks.

(edited 11 years ago)

Reply 1

alwayslast

Try dividing by t (or is it l, cant seem to click on image). Should be able to see a recognisinle type of equation then. You should try substiution.

Posted from TSR Mobile

Reply 2

upthegunners

Original post by alwayslast

Try dividing by t (or is it l, cant seem to click on image). Should be able to see a recognisinle type of equation then. You should try substiution.

Posted from TSR Mobile

the mark seem suggests factoring to get

t(3t^2+5)(t^2-3)=0

but I am not sure how they do this

Reply 3

joostan

Original post by upthegunners

t(3t^4-4t^2-15)=0

Easiest method to solve this?

Thanks.

As before divide by t. Then observe that this is a hidden quadratic
Hint:

Spoiler

Reply 4

Student#123

Original post by upthegunners

Easiest method to solve this?

Thanks.

t=0

or

3t^4-4t^2-15=0

3t^4-4t^2=15

t^2(3t^2-4)=15

i dunno really

Reply 5

Student#123

Original post by joostan

As before divide by t. Then observe that this is a hidden quadratic
Hint:

Spoiler

no u do no divide by t as u lose a solution t=0

do not listen to this op

Reply 6

james22

Original post by upthegunners

the mark seem suggests factoring to get

t(3t^2+5)(t^2-3)=0

but I am not sure how they do this

It's how you factorise any other quadratic eqation.

Reply 7

upthegunners

Original post by joostan

As before divide by t. Then observe that this is a hidden quadratic
Hint:

Spoiler

is letting say

a=t^2

and solving a good idea? Then just subbing

t^2

back in?

Reply 8

alwayslast

t(3t^4 - 4t^2 - 15)=0

3t^4 - 4t^2 - 15=0

t^2 = x

3x^2 - 4x - 15=0
(3x+5)(x-3) = 0
So, x= -5/3 or 3

therefore,
t^2= 3
t=Sqrt 3

Reply 9

joostan

Original post by Student#123

no u do no divide by t as u lose a solution t=0

do not listen to this op

The loss of the solution t = 0 only occurs if you don't write it down. It is the obvious solution, once written down, it's not a problem and you're left with a hidden quadratic.