Can someone solve this in a simplest way please?!

That's a pretty neat method, Alan....I haven't seen it before.....!!!

If my teacher explains as you do I would get full marks every time!! Thanks for the time and effort I appreciate that. 

Thanks. It’s a method I’ve only seen used on cubic equations before - to eliminate the x² term. I guess the quartic specified here was deliberately chosen to simplify enough that it would be easy to find the roots of the resulting transformed function.