x-43=(30-x)-48
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a, x - 43 = ( 35 - x ) - 48
\(x-43=35-x-48\)
\(x+x=35-48+43\)
\(2x=30\)
\(x=15\)
b, 305 - x + 14 = 48 + ( x - 23 )
\(305-x+14=48+x-23\)
\(-x-x=48-23-14-305\)
\(-2x=-294\)
\(x=147\)
c, ( x - 6 + 85 ) = ( x + 51 ) - 54
\(x-6+85=x+51-54\)
\(x-x=51-54-85+6\)
\(0=-82\)
\(x\in\varnothing\)
d, -( 35 - x ) - ( 37 - x ) = 33 - x
\(-35+x-37+x=33-x\)
\(x+x+x=33+37+35\)
\(3x=105\)
\(x=35\)
e, - 12. ( x - 5 ) + 7 . ( 3 - x ) = 5
\(-12x+60+21-7x=5\)
\(-12x-7x=5-21-60\)
\(-19x=-76\)
\(x=4\)
f, 30. ( x+ 2 ) - 6 . ( x - 5 ) - 24 = 100
\(30x+60-6x+30-24=100\)
\(30x-6x=100+24-30-60\)
\(24x=34\)
\(x=\frac{17}{12}\)
chúc bạn học tốt
\(x\) + (-31) - (42) = -45
\(x\) - (31 + 42) = -45
\(x\) - 73 = -45
\(x\) = -45 + 73
\(x\) = 28
305 - \(x\) + 14 = 48 + (\(x\) - 23)
(305 + 14) - \(x\) = (48 - 23) + \(x\)
319 - \(x\) = 25 + \(x\)
\(x\) + \(x\) = 319 - 25
2\(x\) = 294
\(x\) = 294 : 2
\(x\) = 147
\(x-43=\left(35-x\right)\) - 48
\(x\) - 43 = 35 - \(x\) - 48
\(x\) - 43 = - (48 - 35) - \(x\)
\(x\) - 43 = - 13 - \(x\)
\(x\) + \(x\) = -13 + 43
2\(x\) = 30
\(x\) = 30 : 2
\(x\) = 15
x + (-31) - 42 = -45
x - 73 = -45
x = -45 + 73
x = 28
-------
305 - x + 14 = 48 + (x - 23)
319 - x = 48 + x - 23
-x - x = 25 - 319
-2x = -294
x = -294 : (-2)
x = 147
--------
x - 43 = (35 - x) - 48
x = 35 - x - 48 + 43
x + x = 30
2x = 30
x = 30 : 2
x = 15
a)
\(=\frac{7\cdot7\cdot8\cdot8\cdot9\cdot9\cdot10\cdot10\cdot11\cdot11}{6\cdot8\cdot7\cdot9\cdot8\cdot10\cdot9\cdot11\cdot10\cdot12}\)
\(=\frac{7\cdot11}{6\cdot12}\)
\(=\frac{77}{72}\)
b)
\(=1+\frac{1}{6}+1+\frac{1}{12}+1+\frac{1}{20}+1+\frac{1}{30}+1+\frac{1}{42}+1+\frac{1}{56}\)
\(=6+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+\frac{1}{5\cdot6}+\frac{1}{6\cdot7}+\frac{1}{7\cdot8}\)
\(=6+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{7}-\frac{1}{8}\)
\(=6+\frac{1}{2}-\frac{1}{8}\)
\(=6+\frac{3}{8}\)
\(=\frac{51}{8}\)
Chia thành...a và b nhé.
Bg
a)Ta có: \(\frac{49}{48}.\frac{64}{63}.\frac{81}{80}.\frac{100}{99}.\frac{121}{120}\)
= \(\frac{49.64.81.100.121}{48.63.80.99.120}\)
= \(\frac{7.7.8.8.9.9.10.10.11.11}{6.8.7.9.8.10.9.11.10.12}\)
= \(\frac{7.11}{6.12}\) (chịt tiêu trên dưới)
= \(\frac{77}{72}\)
b) Ta có: \(\frac{7}{6}+\frac{13}{12}+\frac{21}{20}+\frac{31}{30}+\frac{43}{42}+\frac{57}{56}\)
Có 6 số hạng (đếm)
= \(1+\frac{1}{6}+1+\frac{1}{12}+1+\frac{1}{20}+1+\frac{1}{30}+1+\frac{1}{42}+1+\frac{1}{56}\)
= \(1+1+...+1+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}\)
= \(1.6+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}\)
= \(6+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}\)
= \(6+\frac{1}{2}-\frac{1}{8}\)
= \(\frac{13}{2}-\frac{1}{8}\)
= \(\frac{51}{8}\)
Hơi dài....
\(d)\)\(43.78-43.48+30.80-30.23\)
\(=\)\(43.\left(78-48\right)+30.\left(80-23\right)\)
\(=\)\(43.30+30.57\)
\(=\)\(30.\left(43+57\right)\)
\(=\)\(30.100\)
\(=\)\(3000\)
\(43\times78-43\times48+30\times80-30\times23\)
\(=43\left(78-48\right)+30\times80-30\times23\)
\(=43\times30+30\times80-30\times23\)
\(=30\left(43+80-23\right)=30.100=3000\)
Đáp án cần chọn là: B
x–43=(35−x)−48
x–43=35–x−48
x+x=35–48+43
2x=30
x=15
\(2x-48=157-\left(-43+69\right)\)
\(2x-48=157-26\)
\(2x-48=131\)
\(2x=131+48\)
\(2x=179\)
\(x=\dfrac{179}{2}\)
\(31.82+125.48+31.43-125.67\)
\(=31\left(82+43\right)-125\left(67-48\right)\)
\(=31.125-125.19\)
\(=125.12\)
\(=1500\)
\(x-43=\left(30-x\right)-48\\ x-43=30-x-48\\ x+x=30-43+48\\ 2x=25\\ x=\dfrac{25}{2}\)
x-43 = ( 30-x ) -48
x-43 = 30-x-48
x+x = 30-48+43
2x = 25
x = \(\dfrac{25}{2}\)= 12,5