下列去括号正确吗?如有错误请改正 (1)-(-a-b)=ab a+b (2)5x-(2x-1)-x2=5x-2x+1+x2 5x-2x+1-x2
下列去括号正确吗？如有错误请改正。 (1)-(-a-b)=a-b (2)5x-(2x-1)-x 2=5x-2x+1+x2 × × a+b 5x-2x+1-x 2
计算 (1)(3a+4b)+(a+b) 解:原式=3a+4b+a+b =4a+5b (2)x+2y-(-2xy) 解:原式=x+2y+2x+y =3x+3y
(2)x+2y-(-2x-y) (1) (3a+4b)+(a+b) =4a+5b 解：原式=3a+4b+a+b 计算： 解：原式=x+2y+2x+y =3x+3y