bài 1 C=7^4.3-7^3/7^4.6-7^3.2 Bài2 c, (2x+1).(x^2-1/4)=0

Giải thích các bước giải:

Bài `1`
`C=(7^4 . 3-7^3)/(7^4 . 6-7^3 . 2)`
`C=(7^3 .7 .3-7^3 .1)/(7^3 .7 .6-7^3 .2)`
`C=(7^3 .21 -7^3 .1)/(7^3 . 42-7^3 .2)`
`C=(7^3.(21-1))/(7^3.(42-2))`
`C=(7^3 . 20 )/(7^3 .40)`
`C=(7^3 .20)/(7^3 .2 .20)`
`C=1/2`
Bài `2`
`(2x+1).(x^2-1/4)=0`
`=>`\(\left[ \begin{array}{l}2x+1=0\\x^2 -\dfrac{1}{4}=0\end{array} \right.\) 
`=>`\(\left[ \begin{array}{l}2x=0+1\\x^2=0+\dfrac{1}{4}\end{array} \right.\) 
`=>`\(\left[ \begin{array}{l}2x=1\\x^2=\dfrac{1}{4}\end{array} \right.\) 
`=>`\(\left[ \begin{array}{l}x=1:2\\x^2=(±\dfrac{1}{2})^2\end{array} \right.\) 
`=>`\(\left[ \begin{array}{l}x=\dfrac{1}{2}\\x=±\dfrac{1}{2}\end{array} \right.\)