tính 3/4 – 1/8 + / -5/ / -4/ – 3/2 + 5/3 1/2 – 3/8 + /-5/4 / 1/4 – 3 + 3/4
tìm x biết
a ) -1/5 + x = / -1 một phần hai / b ) x- /-3/5 / =/ -3 /8/
c ) / x-1/ = 1/2
tính 3/4 – 1/8 + / -5/ / -4/ – 3/2 + 5/3 1/2 – 3/8 + /-5/4 / 1/4 – 3 + 3/4
tìm x biết
a ) -1/5 + x = / -1 một phần hai / b ) x- /-3/5 / =/ -3 /8/
c ) / x-1/ = 1/2
Đáp án:
Giải thích các bước giải:
Đáp án:
1. Tính
`\frac{3}{4} – \frac{1}{8} + | -5|`
`=\frac{3}{4} – \frac{1}{8} + 5`
`=\frac{6}{8} – \frac{1}{8} + \frac{40}{8}`
`=\frac{45}{8}`
`|-4| – \frac{3}{2} + \frac{5}{3}`
`=4 – \frac{3}{2} + \frac{5}{3}`
`= \frac{24}{6} – \frac{9}{6} + \frac{10}{6}`
`= \frac{25}{6} `
`\frac{1}{2} – \frac{3}{8} + |-\frac{5}{4}|`
`=\frac{1}{2} – \frac{3}{8} + \frac{5}{4}`
`=\frac{4}{8} – \frac{3}{8} + \frac{10}{8}`
`=\frac{11}{8} `
`\frac{1}{4} – 3 + \frac{3}{4}`
`=(\frac{1}{4} + \frac{3}{4}) – 3`
`= 1 – 3`
`= – 2`
2. Tìm x
a) `-\frac{1}{5} + x = |-1\frac{1}{2}|`
`-\frac{1}{5} + x = \frac{3}{2}`
` x = \frac{3}{2} + \frac{1}{5} `
` x = \frac{17}{10} `
Vậy ` x = \frac{17}{10} `
b) `x – |-\frac{3}{5}| = |-\frac{3}{8}|`
`x – \frac{3}{5} = \frac{3}{8}`
`x = \frac{3}{8} + \frac{3}{5}`
`x = \frac{39}{40} `
Vậy `x = \frac{39}{40} `
c) `|x – 1| = \frac{1}{2}`
⇔ \(\left[ \begin{array}{l}x – 1 = \frac{1}{2}\\x – 1 = -\frac{1}{2}\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x = \frac{3}{2}\\x = \frac{1}{2}\end{array} \right.\)
Vậy `x ∈ {\frac{3}{2} ; \frac{1}{2}}`