Need with an essay and it cant look like plagiraism.

how could using multiple methods of organization strengthen your expository writing? how could using multiple methods weaken your writing?

Depending not on what method you use can depend on whether you stengthen or weaken the writing. Some methods of organization is good for the writing.
For example:
Putting the opinions in the conclusion paragraph,and the facts for the middle paragraphs,and the opening can be some facts you discovered to get the reader interested or wanting to read you story/essay more.

There are also some bad ways of organizing your essay.
For example:
Nit organizing at all and everything be all over the place. Or even just putting opinions in the facts that dont go together. Or cramping facts that don't belong together in the same paragraph. So using a method that helps strengthen your essay is better then one that'll weaken it. Hope this helped even just alittle have a nice day.