下列运算正确的是( )A.(x+3y)(x-3y)=x2-3y2B.(x+3y)(x-3y)=x2-9y2C.(-x+3y)(x-3y)=-x2-9y2D.(
题型:单选题难度:简单来源:不详
下列运算正确的是( )A.(x+3y)(x-3y)=x2-3y2 | B.(x+3y)(x-3y)=x2-9y2 | C.(-x+3y)(x-3y)=-x2-9y2 | D.(-x-3y)(x+3y)=x2-9y2 |
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答案
A、(x+3y)(x-3y)=x2-9y2,故选项错误; B、正确; C、(-x+3y)(x-3y)=-x2-9y2+6xy,故选项错误; D、(-x-3y)(x+3y)=-x2-9y2-6xy,故选项错误. 故选B. |
举一反三
如果x+y=-1,x-y=-3,那么x2-y2=______. |
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