Tìm x, biết
x-12/4=1/2
36/x+7=12/5
3x+11/8=-1/2
|x+1|/8=1/2
x+3/9=2x-5/10
x.2/3+x.1/3=11/5+(-1/5)
|x|=2 thì x^2=?
Tìm x, biết
x-12/4=1/2
36/x+7=12/5
3x+11/8=-1/2
|x+1|/8=1/2
x+3/9=2x-5/10
x.2/3+x.1/3=11/5+(-1/5)
|x|=2 thì x^2=?
Đáp án + giải thích bước giải :
`1) (x- 12)/4 = 1/2`
`-> (x – 12) . 2 = 4`
`-> x- 12 = 2`
`-> x = 14`
`2) 36/(x + 7) = 12/5`
`-> 36 . 5 = (x + 7) .12`
`-> (x + 7) . 12 = 180`
`-> x + 7 = 15`
`-> x = 8`
`3) (3x + 11)/8 = (-1)/2`
`-> (3x + 11) . 2 = -8`
`-> 3x + 11 = -4`
`-> 3x = -15`
`-> x= -5`
`4) |x + 1|/8 = 1/2`
`-> |x + 1| . 2 = 8`
`-> |x + 1| = 4`
`-> x + 1 = 4` hoặc `x + 1 = -4`
`-> x = 3` hoặc `x = -5`
`5) (x + 3)/9 = (2x – 5)/10`
`-> (x + 3) . 10 = 9 . (2x – 5)`
`-> 10x + 30 = 18x – 45`
`-> 10x – 18x = -30 – 45`
`-> -8x = -75`
`-> x= 75/8`
`6) (x . 2)/3 + (x . 1)/3 = 11/5 + (-1/5)`
`-> (2x)/3 + x/3 = 2`
`-> 2x + x = 2`
`-> 3x = 2`
`-> x = 2/3`
`|x| = 2`
`-> |x^2| = 2^2`
`-> x^2= 2^2` hoặc `x^2 = (-2)^2`
`-> x = 2` hoặc `x = -2`
Đáp án:
Giải thích các bước giải:
$\displaystyle \begin{array}{{>{\displaystyle}l}} 1.\ x-\frac{12}{4} =\frac{1}{2}\\ \Longrightarrow \ x=\frac{1}{2} +\ \frac{12}{4}\\ \Longrightarrow \ x\ =\frac{7}{2}\\ 2.\ \frac{36}{x+7} =\frac{12}{5}\\ ĐK\ x\ khác\ -7\\ \Longrightarrow \ 12( x+7) =5.36\\ \Longrightarrow \ 12x+84=180\\ \Longrightarrow \ x=8( tm)\\ 3.\ 3x+\frac{11}{8} =-\frac{1}{2}\\ \Longrightarrow \ 3x=-\frac{15}{8}\\ \Longrightarrow \ x=\frac{-5}{8}\\ 4.\ \frac{|x+1|}{8} =\frac{1}{2}\\ \Longrightarrow \ |x+1|=4\\ \Longrightarrow \ x+1=4\ ( \ nếu\ x\geqslant -1) \ hoặc\ x+1=-4\ ( nếu\ x< \ -1)\\ \Longrightarrow \ x=3\ ( tm) \ hoặc\ x=-5\ ( tm)\\ 5.\ x+\frac{3}{9} =2x-\frac{5}{ \begin{array}{{>{\displaystyle}l}} 10\\ \end{array}}\\ \Longrightarrow \ x=\frac{3}{9} +\frac{5}{10\ } =\frac{5}{6}\\ 6.\ \frac{2}{3} x+\frac{1}{3} x=\frac{11}{5} -\frac{1}{5}\\ \Longrightarrow \ x=2\\ 7.\ |x|=2\ \Longrightarrow \ x^{2} =2^{2} =4 \end{array}$