X * 5 + X * 5=20
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![](https://rs.olm.vn/images/avt/0.png?1311)
a) 3 x 5 < 3 x 6
3 x 5 > 3x 4
b) 3 x 5 = 5 x 3
4 x 6 = 6 x 4
c) 20 : 4 > 20 : 5
20 : 4 < 20 : 2
![](https://rs.olm.vn/images/avt/0.png?1311)
Hướng dẫn giải:
a) 3 x (20 – 5)
Cách 1:
3 x (20 – 5) = 3 x 15 = 45
Cách 2:
3 x (20 – 5) = 3 x 20 – 3 x 5 = 60 – 15 = 45
b) 20 x (40 – 1)
Cách 1:
20 x (40 – 1) = 20 x 39 = 780
Cách 2:
20 x (40 – 1) = 20 x 40 – 20 x 1 = 800 – 20 = 780
20 x 1 + 20 x 2 + 20 x 3 + 20 x 4 + 20 x 5 + 20 x 6 = ?
1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x ... x 100 = ?
![](https://rs.olm.vn/images/avt/0.png?1311)
20x1+20x2+20x3+20x4+20x5+20x6= 20x(1+2+3+4+5+6)= 20 x 21 = 420
Còn câu 2 mik thấy khó quá cho mik xin lỗi nha
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1) \(2^3\times x-5^2\times x=2\times\left(5^2+2^2\right)-33\)
\(x\times\left(2^3-5^2\right)=2\times\left(25+4\right)-33\)
\(x\times\left(8-25\right)=2\times29-33\)
\(x\times-17=25\)
\(x=-\dfrac{25}{17}\)
2) \(15\div\left(x+2\right)=\left(3^3+3\right)\div1\)
\(15\div\left(x+2\right)=\left(27+3\right)\div1\)
\(15\div\left(x+2\right)=30\div1\)
\(15\div\left(x+2\right)=30\)
\(x+2=\dfrac{1}{2}\)
\(x=-\dfrac{3}{2}\)
3) \(20\div\left(x+1\right)=\left(5^2+1\right)\div13\)
\(20\div\left(x+1\right)=\left(25+1\right)\div13\)
\(20\div\left(x+1\right)=26\div13\)
\(20\div\left(x+1\right)=2\)
\(x+1=20\div2\)
\(x+1=10\)
\(x=9\)
4) \(320\div\left(x-1\right)=\left(5^3-5^2\right)\div4+15\)
\(320\div\left(x-1\right)=\left(125-25\right)\div4+15\)
\(320\div\left(x-1\right)=100\div4+15\)
\(320\div\left(x-1\right)=25+15\)
\(320\div\left(x-1\right)=40\)
\(x-1=8\)
\(x=9\)
5) \(240\div\left(x-5\right)=2^2\times5^2-20\)
\(240\div\left(x-5\right)=4\times25-20\)
\(240\div\left(x-5\right)=100-20\)
\(240\div\left(x-5\right)=80\)
\(x-5=30\)
\(x=35\)
6) \(70\div\left(x-3\right)=\left(3^4-1\right)\div4-10\)
\(70\div\left(x-3\right)=\left(81-1\right)\div4-10\)
\(70\div\left(x-3\right)=80\div4-10\)
\(70\div\left(x-3\right)=20-10\)
\(70\div\left(x-3\right)=10\)
\(x-3=7\)
\(x=10\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
X*5+X*5=20
X*(5+5) =20
X*10 =20
X=20:2=10
x*5+x*5=20
2(x*5)=20
x*5=20:2
x*5=10
x=10:2
x=2
ai k mh mh k alij
k cho mh nha