Môn Toán Lớp 7: bài1: a) 1/2x-0,75=1 1/3 b) 0,5.(x-1)^2-1/2=-3/8

2 bình luận về “Môn Toán Lớp 7: bài1: a) 1/2x-0,75=1 1/3 b) 0,5.(x-1)^2-1/2=-3/8”

1. a) 1/2x-0,75=1 1/3

   <=> 1/2x=25/12

   <=> 25/6

   b) 0,5.(x-1)^2-1/2=-3/8

   <=> 0,5.(x-1)^2=1/8

   <=> (x-1)^2 = 1/4

   <=>  \(\left[ \begin{array}{l}x-1=1/2 \\x-1 = -1/2\end{array} \right.\)

   <=>  \(\left[ \begin{array}{l}x=3/2 \\x = 1/2\end{array} \right.\)

   Trả lời
2. 1/2x-0,75=1 1/3

   1/2x-3/4=4/3

   1/2x=4/3+3/4

   1/2x=16/12+9/12

   1/2x=25/12

   x=25/12:1/2

   x=25/12.2

   x=25/6

   Vậy  x=25/6

   0,5.(x-1)^2-1/2=-3/8

   1/2.(x-1)^2=-3/8+1/2

   1/2.(x-1)^2=-3/8+4/8

   1/2.(x-1)^2=1/8

   (x-1)^2=1/8:1/2

   (x-1)^2=1/8.2

   (x-1)^2=1/4

   (x-1)^2=(1/2)^2  hoặc  (-1/2)^2

   +)Nếu  (x-1)^2=(1/2)^2

   ⇒x-1=1/2

   x=1/2+1

   x=3/2

   +)Nếu  (x-1)^2=(-1/2)^2

   ⇒x-1=-1/2

   x=-1/2+1

   x=1/2

   Vậy  x∈{3/2;1/2}

   Trả lời