5 | + | 5 | + … + | 5 | = | |
3 x 4 | 4 x 5 | 88 x 89 |
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\(\frac{3}{4}.26\frac{1}{5}.\frac{3}{4}.44\frac{1}{5}=\frac{3}{4}.\frac{131}{5}.\frac{3}{4}.\frac{221}{5}=651,3975\)
a: x-4/5=3/7
=>x=3/7+4/5=43/35
b: x+3/7=4/5
=>x=4/5-3/7=13/35
c: 19/20-x=8/5-3/4
=>19/20-x=32/20-15/20=17/20
=>x=2/20=1/10
d: =>4/5*x=2/21
=>x=2/21:4/5=5/42
e: =>x:7/9=6/8
=>x=6/8*7/9=3/4*7/9=21/36=7/12
f: =>x/6=2/3-1/3=1/3
=>x=2
a: x-4/5=3/7
=>x=3/7+4/5=43/35
b: x+3/7=4/5
=>x=4/5-3/7=13/35
c: 19/20-x=8/5-3/4
=>19/20-x=32/20-15/20=17/20
=>x=2/20=1/10
d: =>4/5*x=11/21
=>x=55/84
e: =>x=6/8*7/9=42/72=7/12
f: =>x/6=2/3-1/3=1/3
=>x=2
`1, -2/9 xx 15/17 + (-2/9) xx 2/17`
`= -2/9 xx (15/17 + 2/17)`
`= -2/9 xx 17/17`
`=-2/9xx1`
`=-2/9`
__
`-5/3 xx 6/5 + (-7/9) xx 3/10`
`= -30/15 + (-21/90)`
`= -2 + (-7/30)`
`=-60/30 +(-7/30)`
`=-67/30`
__
`15/20 xx 7/5 + (-9/7) xx (-6/4)`
`=3/4 xx7/5 + (-9/7) xx(-6/4)`
`= 21/20 + 54/28`
`= 21/20 + 27/14`
`=417/140`
__
`-25/13 xx 5/19 + (-25/13) xx 14/19`
`=-25/13 xx (5/19 +14/19)`
`=-25/13 xx 19/19`
`= -25/13 xx 1`
`=-25/13`
__
`-7/13 xx 13/5 + (-9/7) xx 5/3`
`=-7/5 +(-15/7)`
`=-124/35`
\(a.\)
\(\Leftrightarrow x-5+x-7=-12.\)
\(\Leftrightarrow x=-12+-12\)
\(\Leftrightarrow x=-24\)
\(b.\)
\(\Leftrightarrow3x+2x=-109+44\)
\(\Leftrightarrow5x=-65\)
\(\Rightarrow x=-13\)
\(c.\)
\(\Leftrightarrow2x-10-15+5x=-109\)
\(\Leftrightarrow2x-5x=-109+15+10\)
\(\Leftrightarrow3x=-84\)
\(\Rightarrow x=-28\)
\(d.\)
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\(\frac{5}{3.4}+\frac{5}{4.5}+...+\frac{5}{88.89}=5\left(\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{88.89}\right)\)
\(=5\left(\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{88}-\frac{1}{89}\right)=5\left(\frac{1}{3}-\frac{1}{89}\right)=\frac{430}{267}\)