How do I solve for 't' in the platinum wire resistance problem?

[ibysaiyan]

Homework Statement

Homework Equations

$\Delta R$/ R0 = $\alpha$ $\Delta T$
which goes down to : r-r0 /r0 = alpha (T-T0)
r/r0 = alpha T +1
3. The attempt at the solution

Hi there, I'm on a verge of mental breakdown. I have spent over 2 a4- sheets on figuring out how to get 't'.

I have found out the value r/ro... however the part to find 't' has been daunting... I am aware of the expression within the bracket being a quadratic equation,hence two solutions of 't'... but what becomes of the value of r/r0 ?

Thanks for your help in advance.

 

[ibysaiyan]

Although I have sent my work to be marked but can anyone tell me how I should have proceeded with this question ? Thanks