Can someone help me solve this integral?: http://www.wolframalpha.com/input/?i=integral+(x^6+*+e^(-x^7))+from+-infinity+to+infinity

I get a final answer of 0 but the correct answer is positive infinity. I would just like to know how to get there and what I am doing wrong. (My work is attached)

Any help would be greatly appreciated!

Thanks in advance!