a) 1-5+7-8+4-1+5-7+8

=(1-1) - (-5+5) -(7-7) -(-8+8) +4

=0

b)=-39+9

=-30

c)=(20-20)-(-4+4)-(8-8)-17+15

=-2

d)= (13-13)-(-98+98)-(91-91)-75

=-75

cậu ấn máy tính không được à

Phải trình bày rõ ràng chứ

a) \(1-5+7-8+4-1+5-7+8\)

\(=\left(1-1\right)+\left(5-5\right)+\left(7-7\right)+\left(8-8\right)+4\)

\(=0+0+0+0+4\)

\(=4\)

b) \(12-14+9-3-14+9-3+14-19-9-12\)

\(=\left(12-12\right)+\left(9-9\right)+\left(14-14\right)+9-3-3\)

\(=0+0+0+9-6\)

\(=3\)

c) \(20-4+8-17+4-8-20+15\)

\(=\left(20-20\right)+\left(4-4\right)+\left(8-8\right)+\left(-17+4+15\right)\)

\(=0+0+0+2\)

\(=2\)

\(13-98+91-75+98-91-13\)

\(=\left(13-13\right)+\left(98-98\right)+\left(91-91\right)-75\)

\(=0+0+0-75\)

\(=-75\)

sử dung kết hop

a) \(\frac{45^{10}.5^{20}}{75^{15}}\)

=
\(\frac{\left(5.9\right)^{10}.5^{20}}{\left(5.15\right)^{15}}\)

=  \(\frac{5^{10}.9^{10}.5^{20}}{5^{15}.15^{15}}\)

=    \(\frac{5^{10}.3^{20}.5^{20}}{5^{15}.15^{15}}\)

=    \(\frac{5^{10}.15^{20}}{5^{15}.15^{15}}\)

=     \(\frac{15^5}{5^5}\)

=     \(\frac{3^5.5^5}{5^5}\)

= \(3^5\)

b) \(\frac{\left(0,8\right)^5}{\left(0,4\right)^6}\)

=   \(\frac{\left(0,4\right)^5.2^5}{\left(0,4\right)^6}\)

=    \(\frac{2^5}{0,4}\)

= \(2^5\) : 0,4

(=) 32 : \(\frac{2}{5}\)

= 90

c) \(\frac{2^{15}.9^4}{6^6.8^3}\)

=  \(\frac{2^{15}.\left(3^2\right)^4}{\left(2.3\right)^6.\left(2^3\right)^3}\)

=    \(\frac{2^{15}.3^8}{2^6.3^6.2^9}\)

=   \(3^2\)

=16.15-25.6+1

=240-150+1

=90+1

=91

4².15-5².6+1²⁰²⁰

=16.15-25.6+1

=240-150+1

=90+1

=91

HOC TỐT

4^2.15-5^2.6+1^2020

=16.15-25.6+1

=240-150+1

=90+1

=91

a)  Cách 1 :                                                          Cách 2

1 + 3 +5 + 7 + 9 + 11 + 13 + 15 + 17 + 19             1 + 3 +5 + 7 + 9 + 11 + 13 + 15 + 17 + 19

=(1 + 19) + (3 + 17) +.... + (9 + 11)                   Áp dụng công thức tính dãy số ta có :

= 20 + 20 + ... + 20                                           \(\frac{\left[\left(19-1\right):2+1\right].\left(19+1\right)}{2}=\frac{10.20}{2}=10.10=100\)

= 20 x 5 = 100

b) giống bài a     nhưng cách 1 làm dài lắm , mình sẽ làm cách 2

áp dụng công thức tính dãy số ta có:

\(\frac{\left[\left(200-4\right):4+1\right].\left(200+4\right)}{2}=\frac{50.204}{2}=50.102=5100\)

                         Tong :  \(\frac{\left[200+4\right].50}{2}\) =5100

\(a,\)Đặt \(A=1+2+2^2+...+2^{99}+2^{100}\)

\(\Rightarrow2A=2+2^2+...+2^{100}+2^{101}\)

\(\Rightarrow2A-A=\left(2+2^2+2^3+...+2^{101}\right)-\left(1+2+2^2+...2^{100}\right)\)

\(\Rightarrow A=2^{101}-1\)

\(b,\)Đặt \(B=5+5^3+5^5+...+5^{97}+5^{99}\)

\(\Rightarrow5^2B=5^3+5^5+...+5^{99}+5^{101}\)

\(\Rightarrow25B-B=\left(5^3+5^5+...+5^{99}+5^{101}\right)-\left(5+5^3+...+5^{99}\right)\)

\(\Rightarrow24B=5^{101}-5\)

\(\Rightarrow B=\frac{5^{101}-5}{24}\)

bn hâm mộ cùng phim với mink a

sao sai?