1, Tinh
1 + 1/3 + 1/9 + 1/27 + 1/81
2. Tinh nhanh :
5 m2 7 dm2 + 2,6 m2 + 3,33 m2
3. Tim x :
a, x : 4,37 = 5,6 ( du 1,53 ) b, 13,5 x ( X : 5,6 ) = 36,45
giup mik nha !!!
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\(1,\)
\(a,1+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}\)
\(=\frac{81}{81}+\frac{27}{81}+\frac{9}{81}+\frac{3}{81}+\frac{1}{81}\)
\(=\frac{81+27+9+3+1}{81}\)
\(=\frac{121}{81}\)
\(=1\frac{40}{81}\)
\(b,37,25+4,7.2,3-9,8\)
\(=37,25+10,81-9,8\)
\(=38,26\)
\(2,\)
\(a,x:4,37=5,6\left(dư1,53\right)\)
\(x=5,6.4,37+1,53\)
\(\Rightarrow x=26,002\)
\(b,13,5.\left(x:5,6\right)=36,45\)
\(\left(x:5,6\right)=36,45:13,5\)
\(x:5,6=2,7\)
\(x=2,7.5,6\)
\(\Rightarrow x=15,12\)
a) 4 m2 = 400 dm2
7 m2 = 70 000 cm2
3 m2 = 3 000 000 m2
b) 600 cm2 = 6 dm2
300 dm2 = 3 m2
80 000 mm2 = 800 cm2
c) 1 m2 23 dm2 = 123 dm2
5 m2 3 dm2 = 503 dm2
9 m2 23 cm2 = 90 023 cm2
a) 4 m2 = 400 dm2
7 m2 = 70 000 cm2
3 m2 = 3 000 000 m2
b) 600 cm2 = 6 dm2
300 dm2 = 3 m2
80 000 mm2 = 800 cm2
c) 1 m2 23 dm2 = 123 dm2
5 m2 3 dm2 = 503 dm2
9 m2 23 cm2 = 90 023 cm2
\(\dfrac{1}{2.3}+\dfrac{1}{3.4}+...+\dfrac{1}{49.50}\)
\(=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{49}-\dfrac{1}{50}\)
\(=\dfrac{1}{2}-\dfrac{1}{50}=\dfrac{12}{25}\)
c)\(\left(xy^2-1\right)\left(x^2y+5\right)\)
\(=x^3y^3+5xy^2-x^2y-5\)
d)\(4\left(x-\dfrac{1}{2}\right)\left(x+\dfrac{1}{2}\right)\left(4x^2+1\right)\)
\(=4\left(x^2-\dfrac{1}{4}\right)\left(4x^2+1\right)\)
\(=4\left(4x^4+x^2-x-\dfrac{1}{4}\right)\)
\(=16x^4+4x^2-4x-1\)
a: 3km75m=3,075m
\(\dfrac{1}{4}m^2=25dm^2\)
3h15'=195p
b: 26320:35=752
c: =3/5(5/12+7/12)
=3/5
a, \(3km75m=3075m\)
\(\dfrac{1}{4}m^2=25\text{d}m^2\)
`3` giờ `15` phút = `195` phút
b,
`->26320 : 35=752.`
c, \(\dfrac{9}{15}\times\dfrac{5}{12}+\dfrac{9}{15}\times\dfrac{7}{12}=\dfrac{9}{15}\times\left(\dfrac{5}{12}+\dfrac{7}{12}\right)=\dfrac{9}{15}\times1=\dfrac{9}{15}\)
`@mt`
Mình không biết
ai lam nhanh va dung thi mk cho 15 k