Thực hiện phép tính ( hợp lý nếu có thể ) :
3^10 .10+3^11.5/ 3^9 . 5^2
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\(3^{^{ }2}\) . 5 + 23.10 - 81: 3
= 9.5 + 8.10 - 27
= 45 + 80 - 27
= 125 - 27
= 98
\(3^2\cdot5+2^3\cdot10-81:3\)
\(=9\cdot5+8\cdot10-3^4:3\)
\(=40+80-3^3\)
\(=120-27\)
\(=93\)
(23.94+93.45):(92.10-92)
= ( 8. 94+93.9.5):(81.10-81)
= (8.94+94.5):(810-81)
=[94.(8+5)]:729
=[94.13]:729
=6561.13:729
=6561:729.13
=9.13
=117
Mk nhanh nhat day
(23.94+93.45):(92.10-92)
=(23.94+5.94):(81.10-81)
=[94.(8+5)]:(810-81)
=(6561.13):729
=85296:729
=117
a,\(\frac{7}{10}\cdot\frac{4}{9}+\frac{3}{10}\cdot\frac{4}{9}-1\frac{7}{9}\)
\(=\frac{14}{45}+\frac{2}{15}-\frac{16}{9}\)
\(=\frac{14}{45}+\frac{6}{45}-\frac{80}{45}\)
\(=\frac{-60}{45}=\frac{-4}{3}\)
b,\(\frac{-5}{6}+\frac{4}{9}\cdot\left(\frac{5}{4}-\frac{2}{3}\right)\cdot\left(-3\right)^2+\frac{5}{9}\cdot30\%\)
\(=\frac{-5}{6}+\frac{4}{9}\cdot\left(\frac{7}{12}\right)\cdot9+\frac{5}{9}\cdot\frac{3}{10}\)
\(=\frac{-5}{6}+\frac{7}{3}+\frac{1}{6}\)
\(=\frac{-5}{6}+\frac{14}{6}+\frac{1}{6}\)
=\(=\frac{10}{6}=\frac{5}{3}\)
Câu 9
a) 2/15 + (-3/5)
= 2/15 - 3/5
= 2/15 - 9/15
= -7/15
b) -5/7 + 3/7 . (-2/9)
= -5/7 - 2/21
= -15/21 - 2/21
= -17/21
c) 5/16 - (7/15 - 3/16) + 17/30
= 5/16 - 7/15 + 3/16 + 17/30
= (5/16 + 3/16) + (17/30 - 14/30)
= 1/2 + 1/10
= 5/10 + 1/10
= 6/10
= 3/5
\(a,\dfrac{2}{15}+\left(-\dfrac{3}{5}\right)\\ =\dfrac{2}{15}-\dfrac{3}{5}\\ =\dfrac{2}{15}-\dfrac{9}{15}\\ =-\dfrac{7}{15}\\ b,-\dfrac{5}{7}+\dfrac{3}{7}\times\left(-\dfrac{2}{9}\right)\\ =-\dfrac{5}{7}-\dfrac{2}{21}\\ =-\dfrac{15}{21}-\dfrac{2}{21}\\ =-\dfrac{17}{21}\\ c,\dfrac{5}{16}-\left(\dfrac{7}{15}-\dfrac{3}{16}\right)+\dfrac{17}{30}\\ =\dfrac{5}{16}-\dfrac{7}{15}+\dfrac{3}{16}+\dfrac{17}{30}\\ =\left(\dfrac{5}{16}+\dfrac{3}{16}\right)-\left(\dfrac{17}{15}+\dfrac{17}{30}\right)\\ =\dfrac{1}{2}-\dfrac{17}{10}\\ =\dfrac{5}{10}-\dfrac{17}{10}\\ =-\dfrac{6}{5}.\)
Lời giải:
a. Đề lỗi.
b. $=5(1+2+3+...+19)=5.19(19+1):2=950$
c. $=(100-99)+(98-97)+....+(2-1)=\underbrace{1+1+...+1}_{50}=1.50=50$
d. Theo quy luật của tổng thì:
$=1+4+5+9+14+23+37+60+97=250$
3^10 . 10 + 3^ 11 . 5 / 3^9 . 5^2
= 3^10 . 2 . 5 + 3^10 . 3 . 5 / 3^9 . 5^2
= 3^10 ( 2 . 5 + 3 .5 ) / 3^9 . 5^2
= 3^10 [ 5 ( 2 + 3 ) ] / 3^9 . 5^2
= 3^10 ( 5 . 5 ) / 3^9 . 5^2
= 3^10 . 5^2 / 3^9 . 5^2
= 3^10 / 3^9
= 3^9 . 3 / 3^9
= 3