对于有理数x，y定义新运算：x*y=ax+by-5，其中a，b为常数．已知1*2=-9，（-3）*3=-2，则a-b=____

snake的复数是snakes。

    ____crowd of more than 22,000 people gathered near Las Vegas' famous Mandalay Bay Hotel____the Route 91 Harvest Festival. Without____(expect), from the hotel's 32^nd floor, a gunman opened fire on the people below,____ (kill)59 people and at least 500 injured. It was the most____(dead)shooting in US history. President Donald Trump described____as “an act of pure evil”. He ordered US flags to be____(fly)at half-staff to honor those____died. “In moments of tragedy and horror, America comes together as one. And it always ____(have),” Trump said____(Politician) around the world offered their support for the United States.

如图所示的电路中电源电压保持不变，当滑动变阻器的滑片P向右移动时，下列说法不正确的是