【单选题】已知 x=-2 y=4 和 x=4 y=1 都是方程y=ax+b的解,则a和b的值是( )
【单选题】______ is the best name and description of the vessel referred to.
【简答题】先化简,再求值, (1) 12( a 2 b- 1 3 ab 2 )+5( ab 2 -a 2 b)-4( 1 2 a 2 b+3) ,其中 a= 1 5 ,b=5 ; (2)已知a-b=5,ab=-1,求(2a+3b-2ab)-(a+4b+ab)-(3ab+2b-2a)的值.
【简答题】听短文,填空。 Information Sheet 1 Lin Yu comes from _________ in Shanghai. 2 Lin Yu has such an English name because her mother thought she was _________ an angel. 3 Lin Yu is a little girl and doesn't look...
【单选题】已知 a =(3,4), b =(5,12), a 与 b 的夹角的余弦为( )
【单选题】已知a-2 ab +b=0(a>0,b>0),则 3a- ab +b 5a+3 ab -4b 等于( )