Tìm x
5x+30=110
2x-18=56
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Bạn thử xem lại đề nhé, giữa 3 số này là dấu cộng hay dấu nhân.
Nếu là dấu cộng thì ta có:
Nếu là dấu nhân thì ta có:
1: =66+34-73-27+99=99
2: =54-45+30-54-30+5=-40
3: =42-56+33-33+56-42=0
4: =50-47-50+18+47-18=0
5: =10-28+30-4=2-4+10=12-4=8
\(\text{1.-(-66)+34+(-73)-27+99}.\)
\(=66+34-73-27+99=100-100+99=-99.\)
\(\text{2.54-(45-30+54)-30+5}.\)
\(54-45+30-54-30+5=\left(54-54\right)+\left(-45+5\right)+\left(30-30\right)=-40.\)
\(\text{3.42-56+33-(33-56+42)}.\)
\(=42-56+33-33+56-42=\left(42-42\right)+\left(-56+56\right)+\left(33-33\right)=0.\)
\(\text{4.50-(47+50-18)+(47-18)}.\)
\(=50-47-50+18+47-18=\left(50-50\right)+\left(-47+47\right)+\left(18-18\right)=0.\)
\(\text{5.10-(28-30+4)}.\)
\(=10-28+30-4=10+30-20-8-4=20-12=8.\)
\(\text{6.-(-73)+(44-94+27)+94}.\)
\(=73+44-94+27+94=\left(73+27\right)+\left(-94+94\right)+44=100+44=144.\)
a) \(5x\left(x-7\right)-30\cdot\left(x-7\right)=0\)
\(\Rightarrow\left(5x-30\right)\left(x-7\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}5x-30=0\\x-7=0\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=6\\x=7\end{matrix}\right.\)
b) \(\left(2x-4\right)\left(2x+4\right)-x\left(x+3\right)=3x\left(x+5\right)\)
\(\Rightarrow4x^2-16-x^2-3x=3x^2+15x\)
\(\Rightarrow-16=18x\Rightarrow x=-\dfrac{8}{9}\)
a, Ta có: 10 = 2.5; 12 = 2 2 .3
BCNN(10,12) = 2 2 .3.5 = 60
b, Ta có: 24 = 2 3 .3; 56 = 2 3 .7
BCNN(24;56) = 2 3 .3.7 = 168
c, Ta có: 84 = 2 2 .3.7; 108 = 2 2 . 3 3
BCNN(84;108) = 2 2 . 3 3 .7
d, Ta có: 33 = 3.11; 44 = 4.11; 55 = 5.11
BCNN(33;44;55) = 3.4.5.11 = 660
e, Ta có: 8 = 2 3 ; 18 = 2. 3 2 ; 30 = 2.3.5
BCNN(8,18,30) = 2 3 . 3 2 . 5 = 360
f, Ta có: 40 = 2 3 . 5 ; 28 = 2 2 .7; 140 = 2 2 .5.7
BCNN(40;28;140) = 2 3 . 5 . 7 = 280
\(\frac{1}{3}-\left(\frac{1}{3.4}-\frac{1}{4.5}-...-\frac{1}{7.8}\right)=x-\frac{5}{18}\)
\(x-\frac{5}{18}=\frac{1}{3}-\left(\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{7}-\frac{1}{8}\right)\)
\(x-\frac{5}{18}=\frac{1}{3}-\frac{1}{3}+\frac{1}{8}\)
\(x-\frac{5}{18}=0+\frac{1}{8}\)
\(x-\frac{5}{18}=\frac{1}{8}\)
\(x=\frac{1}{8}+\frac{5}{18}\)
\(x=\frac{9}{72}+\frac{20}{72}\)
\(x=\frac{29}{72}\)
1/3 - 1/12 - 1/20 - 1/30 - 1/42 - 1/56 = x - 5/18
1/4 - 1/20 - 1/30 - 1/42 - 1/56 = x - 5/18
1/5 - 1/30 - 1/42 - 1/56 = x - 5/18
1/6 - 1/42 - 1/56 = x - 5/18
1/7 - 1/56 = x - 5/18
1/8 = x - 5/18
x=1/8+5/18
x= 29/72
Vậy : x = 29/72
a, \(5x+30=110\)
\(5x=110-30\)
\(5x=80\)
\(x=80:5\)
\(x=16\)
b, \(2x-18=56\)
\(2x=56+18\)
\(2x=74\)
\(x=74:2\)
\(x=37\)
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