(5/10×12)+(5/12×14)+...+(5/146×148)= bao nhiêu
Giúp em với ạ.
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17 tháng 8 2021
a: \(\sqrt{5+2\sqrt{6}}=\sqrt{3}+\sqrt{2}\)
b: \(\sqrt{12+2\sqrt{35}}-\sqrt{12-2\sqrt{35}}=\sqrt{7}+\sqrt{5}-\sqrt{7}+\sqrt{5}=2\sqrt{5}\)
c: \(\sqrt{16+6\sqrt{7}}=4+\sqrt{7}\)
d: \(\sqrt{31-12\sqrt{3}}=3\sqrt{3}-2\)
e: \(\sqrt{27+10\sqrt{2}}=5+\sqrt{2}\)
f: \(\sqrt{14+6\sqrt{5}}=3+\sqrt{5}\)
G
13 tháng 9 2020
a)\(\frac{7}{12}.\frac{6}{11}+\frac{7}{12}.\frac{5}{11}-2\frac{7}{12}\)
\(=\frac{7}{12}.\left(\frac{6}{11}+\frac{5}{11}\right)-\frac{31}{12}\)
\(=\frac{7}{12}-\frac{31}{12}\)
\(=-2\)
b)\(\frac{-5}{9}.\frac{-6}{13}+\frac{5}{-9}.\frac{-5}{13}-\frac{5}{9}\)
\(=\frac{5}{9}.\left(\frac{6}{13}+\frac{5}{13}-1\right)\)
\(=\frac{5}{9}.\left(\frac{11}{13}-\frac{13}{13}\right)\)
\(=\frac{5}{9}.\frac{-2}{13}\)
\(=-\frac{10}{117}\)
c)\(0,8.\frac{-15}{14}-\frac{4}{5}.\frac{13}{14}-1\frac{2}{5}\)
\(=\frac{4}{5}.\frac{-15}{14}-\frac{4}{5}.\frac{13}{14}-\frac{7}{5}\)
\(=\frac{4}{5}.\left(-\frac{15}{14}-\frac{13}{14}\right)-\frac{7}{5}\)
\(=\frac{4}{5}.\left(-2\right)-\frac{7}{5}\)
\(=\frac{-8}{5}-\frac{7}{5}\)
\(=-3\)
d)\(-75\%.\frac{6}{7}+5\%.\frac{6}{7}+\frac{7}{10}.1\frac{1}{7}\)
\(=\frac{-15}{20}.\frac{6}{7}+\frac{1}{20}.\frac{6}{7}+\frac{7}{10}.\frac{8}{7}\)
\(=\frac{6}{7}.\left(\frac{-15}{20}+\frac{1}{20}\right)+\frac{4}{5}\)
\(=\frac{6}{7}.\frac{-7}{10}+\frac{4}{5}\)
\(=-\frac{3}{5}+\frac{4}{5}\)
\(=\frac{1}{5}\)
Linz
NA
2
9 tháng 3 2020
a) (-8)+10+(-12)+14+...+(-32)+34+(-36)+38
=(-8+10)+(-12+14)+...+(-32+34)+(-36+38)
=2+2+...+2+2 ( Có 16 số 2)
=2.16
=32
G
9 tháng 3 2020
Trả lời:
\(a)\)\(\left(-8\right)+10+\left(-12\right)+14+...+\left(-32\right)+34+\left(-36\right)+38\)(Có 16 số)
\(=\left[\left(-8\right)+10\right]+\left[\left(-12\right)+14\right]+...+\left[\left(-36\right)+38\right]\)(Có 8 nhóm)
\(=\left(-2\right)+\left(-2\right)+...+\left(-2\right)\)
\(=\left(-2\right).8\)
\(=-16\)
\(b,\)\(1+3+5+...+49-2-4-6-...-50\)
\(=\left(1-2\right)+\left(3-4\right)+...+\left(49-50\right)\)(Có 25 nhóm)
\(=\left(-1\right)+\left(-1\right)+...+\left(-1\right)\)
\(=\left(-1\right).25\)
\(=-25\)
Hok tốt!
Good girl
7 tháng 6 2017
( 2 x y + 2/15 ) x 3 = 4/5
( 2 x y + 2/15 ) = 4/5 : 3
( 2 x y + 2/15 ) = 4/15
2 x y = 4/15 - 2/15
2 x y = 2/15
y = 2/15 :2
y = 1/15
DP
7 tháng 6 2017
(2 x y + 2/15) x 3 = 4/5
2 x y + 2/15) = 4/5 : 3
2 x y + 2/15 = 4/15
2 x y = 4/15 - 2/15
2 x y = 2/15
y = 2/15 : 2
y = 1/15
7/9 x (2 - 1/3 x y) = 14/15
(2 - 1/3 x y) = 14/15 : 7/9
(2 - 1/3 x y) = 6/5
2 - y = 6/5 x 1/3
2 - y = 2/5
y = 2/5 + 2
y = 12/5
4/21 + 5 x y - 8/7 = 1/3
4/21 + 5 x y = 1/3 + 8/7
4/21 + 5 x y = 31/21
5 x y = 31/21 - 4/21
5 x y = 9/7
y = 9/7 : 5
y = 9/35
7/12 x y - 3/12 x y = 5
y x (7/12 - 3/12) = 5
y x 1/3 = 5
y = 5 : 1/3
y = 15
CM
27 tháng 1 2017
Trung bình mỗi em học sinh cao số cm lag
(148 + 146 +144 + 142 + 140 ) : 5 = 144 (cm)
Đáp số: 144 cm
\(\left(\frac{5}{10\cdot12}\right)+\left(\frac{5}{12\cdot14}\right)+...+\left(\frac{5}{146\cdot148}\right)\)
\(=5\left[\frac{1}{10\cdot12}+\frac{1}{12\cdot14}+...+\frac{1}{146\cdot148}\right]\)
\(=5\left[\frac{1}{10}-\frac{1}{12}+\frac{1}{12}-\frac{1}{4}+...+\frac{1}{146}-\frac{1}{148}\right]\)
\(=5\left[\frac{1}{10}-\frac{1}{148}\right]\)
\(=5\cdot\frac{69}{740}\)
\(=\frac{69}{148}\)
Không chắc nhá (:
@Trần Nhật Quỳnh@ lag
\(\frac{5}{10\cdot12}+\frac{5}{12\cdot14}+...+\frac{5}{146\cdot148}\)
\(=\frac{5}{2}\left(\frac{2}{10\cdot12}+\frac{2}{12\cdot14}+....+\frac{2}{146\cdot148}\right)\)
\(=\frac{5}{2}\left(\frac{1}{10}-\frac{1}{12}+\frac{1}{12}-\frac{1}{14}+...+\frac{1}{146}-\frac{1}{148}\right)\)
\(=\frac{5}{2}\left(\frac{1}{10}-\frac{1}{148}\right)\)