\(S=2.10+2.12+2.14+...+2.20\\ S=2.\left(10+12+14+...+20\right)\\ S=2.\left\{\left[\left(20-10\right):2+1\right].\left(20+10\right):2\right\}\\ S=2.\left\{\left[10:2+1\right].30:2\right\}\\ S=2.\left\{\left[5+1\right].30:2\right\}\\ S=2.\left\{6.30:2\right\}\\ S=2.\left\{180:2\right\}\\ S=2.90\\ S=180\)

TK :

S=2.10+2.12+2.14+...+2.20

S=2.[(10+20)+(12+18)+(14+16)]

S=2.(30+30+30)

S=2.90

S=180

Ta có: \(B=\frac{5^2.6^{11}.16^2+6^2.12^6.15^2}{2.6^{12}.10^4-81^2.960^3}=\frac{5^2.\left(2.3\right)^{11}.\left(4^2\right)^2+\left(2.3\right)^2.\left(2^2.3\right)^6.\left(3.5\right)^2}{2.\left(2.3\right)^{12}.\left(2.5\right)^4-\left(3^4\right)^2.\left(2^6.3.5\right)^3}\)

\(\frac{5^2.2^{11}.3^{11}.2^8+2^2.3^2.2^{12}.3^6.3^2.5^2}{2.2^{12}.3^{12}.2^4.5^4-3^8.2^{18}.3^3.5^3}=\frac{5^2.2^{19}.3^{11}+2^{14}.3^{10}.5^2}{2^{17}.3^{12}.5^4-3^{11}.2^{18}.5^3}\)

\(=\frac{5^2.2^{14}.3^{10}.\left(2^5.3+1\right)}{2^{17}.3^{11}.5^3.\left(3.5-2\right)}=\frac{2^{14}.3^{10}.5^2.97}{2^{17}.3^{11}.5^3.13}=\frac{1.1.1.97}{2^3.3.5.13}=\frac{97}{1560}\)

\(B=\frac{5^2.6^{11}.16^2+6^2.12^6.15^2}{2.6^{12}.10^4-81^2.960^3}\)

\(B=\frac{5^2.2^{11}.3^{11}.2^{4^2}+2^2.3^2.2^{2^6}.3^6.3^2.5^2}{2.2^{12}.3^{12}.10^4-3^{4^2}.2^{5^3}.3^3}\)

\(B=\frac{5^2.2^{11}.2^8.3^{11}+2^2.2^{12}.3^2.3^6.3^2.5^2}{2^{13}.3^{12}.10^4-3^8.3^3.2^{15}}\)

\(B=\frac{5^2.2^{19}.3^{11}+2^{14}.3^{10}.5^2}{2^{13}.3^{12}.10^4-3^{11}.2^{15}}\)

\(B=\frac{5^2.2^{14}.3^{10}.\left(2^5.3+1\right)}{2^{13}.3^{11}.\left(3.10^4-2^2\right)}\)

\(B=\frac{5^2.2^{14}.3^{10}.97}{2^{13}.3^{11}.29996}\)

\(B=\frac{5^2.2.97}{3.29996}\)

\(B=\frac{4850}{89988}\)

\(B=\frac{2425}{44994}\)

leminhduc giải sai rồi

Mình nhìn vào cách làm đã biết rồi

Kết quả không đúng đâu

\(S=2\cdot10+2\cdot12+2\cdot14+...+2\cdot20\)

\(S=2\cdot\left(10+12+14+16+18+20\right)\)

\(S=2\cdot\left[\left(20+10\right)\cdot6:2\right]\)

\(S=2\cdot90=180\)

\(S=2\cdot10+2\cdot12+2\cdot14+\dots+2\cdot20\\=2\cdot(10+12+14+\dots+20)\)

Đặt \(A=10+12+14+\dots+20\)

Số các số hạng của $A$ là:

$(20-10):2+1=6$ (số)

Tổng $A$ bằng:

$(20+10)\cdot6:2=90$

Thay $A=90$ vào $S$, ta được:

$S=2\cdot90=180$

S=300

Tính bình thường nhé b

S = 2.10 + 2.12 + 2.14 +...+ 2.20

S = 2.10 + 2.12 + 2.14 + 2.16 + 2.18 + 2.20

S = 20 + 24 + 28 + 32 + 36 + 40

S =(20 + 40) + (24 + 36) + (28 + 32)

S = 60 + 60 + 60

S = 180

ai làm được mình tick cho

a)=1

b)=3

tickkkkkkk

A, =1000

B, =\(\frac{101}{1440}\)

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