题目

The biggest challenge faced by travelers especially those who like to have a hiking trip is how to ensure a steady supply of clean clothes. Now, thanks to a great invention called Scrubba Wash Pack, that worry may be a thing of the past.The portable(手提的) washing machine was invented by Ash Newland in 2010, while planning to climb Mt. Kilimanjaro. Struck by the limited packing space, he got inspiration(灵感) from traditional washboards to create a bag that could be used to clean clothes. Then he gave up his career as a lawyer and focused on perfecting the bag’s design. By 2012, the ba分解因式：-9x2+4=（    ）。