解方程 (带△本题要验算) (1)4.2x-2.7×4=6 (2)0.8x+x=5.4 (3)△3.2-0.16x=0.

问题描述:

解方程 (带△本题要验算)
(1)4.2x-2.7×4=6           
(2)0.8x+x=5.4
(3)△3.2-0.16x=0.

(1)4.2x-2.7×4=6
          4.2x-10.8=6
     4.2x+10.8-10.8=6+10.8
               4.2x=16.8
           4.2x÷4.2=16.8÷4.2
                   x=4
(2)0.8x+x=5.4
       1.8x=5.4
  1.8x÷1.8=5.4÷1.8
          x=3
 (3)3.2-0.16x=0
3.2+0.16x-0.16x=0.16x
    0.16x÷0.16=3.2÷0.16
              x=20
验算:
方程的左边
=3.2-0.16x
=3.2-0.16×20
=3.2-3.2
=0
右边=0
所以方程的左边=方程的右边.
所以x=20是方程的解.