合并同类项并求值
x-{-5x-[-y+(-x+3y)+x]}, 其中3x+y=1
合并同类项并求值
x-{-5x-[-y+(-x+3y)+x]}, 其中3x+y=1
x-{-5x-[-y+(-x+3y)+x]},
=x-[-5x-(-y-x+3y+x)]
=x-(-5x-2y)
=x+5x+2y
=6x+2y
=2(3x+y)
=2
解:x-{5x-[-y+(-x+3y)+x]}
去大括号:x-[-5x-(-y-x+3y+x)]
去中括号:x-(-5x-2y)
去小括号:x+5x+2y
合并同类项:6x+2y
变换成:2(3x+y)
把3x+y=1代入2(3x+y)中
得:2×1=2
x-{-5x-[-y+(-x+3y)+x]}
=x+5x-y+x+3y-x
=6x+2y
=2(3x+y)
=2*1
=2