Bài 130 trang 32 SBT toán 7 tập 1

Đề bài

Tìm \(x\), biết:

a) \(\displaystyle {1 \over 4} + x = {{ - 1} \over 3}\)   

b) \(\displaystyle - {3 \over 7} + x = {5 \over 8}\)

c) \(0,472 - x = 1,634\) 

d) \(\displaystyle - 2,12 - x = 1{3 \over 4}\)

Lời giải

a) \(\displaystyle {1 \over 4} + x = {{ - 1} \over 3}\)

\(\displaystyle x =  - {1 \over 3} - {1 \over 4}\)

\(\displaystyle  x = {{ - 4} \over {12}} + {{ - 3} \over {12}} \)

\(\displaystyle x =  - {7 \over {12}}\) 

b) \(\displaystyle  - {3 \over 7} + x = {5 \over 8} \)

\(\displaystyle x = {5 \over 8} + {3 \over 7} \)

\(\displaystyle x = {{35} \over {56}} + {{24} \over {56}} \)

\(\displaystyle x = {{59} \over {56}}\) 

c) \(0,472 - x = 1,634 \)

\(x = 0,472 - 1,634 \)

\(x =  - 1,162\) 

d) \(\displaystyle - 2,12 - x = 1{3 \over 4}\)

\(\displaystyle x =  - 2,12 - 1{3 \over 4} \)

\( x =  - 2,12 - 1,75 \)

\(x =  - 3,87\) 


Quote Of The Day

“Two things are infinite: the universe and human stupidity; and I'm not sure about the universe.”