1/

Tổng A là tổng các số hạng cách đều nhau 4 đơn vị.

Số số hạng: $(101-1):4+1=26$

$A=(101+1)\times 26:2=1326$

2/

$B=(1+2+2^2)+(2^3+2^4+2^5)+(2^6+2^7+2^8)+(2^9+2^{10}+2^{11})$

$=(1+2+2^2)+2^3(1+2+2^2)+2^6(1+2+2^2)+2^9(1+2+2^2)$

$=(1+2+2^2)(1+2^3+2^6+2^9)$

$=7(1+2^3+2^6+2^9)\vdots 7$

\(A=\frac{7}{3\cdot13}+\frac{7}{13\cdot23}+\cdots+\frac{7}{53\cdot63}\)

\(=\frac{7}{10}\left(\frac{10}{3\cdot13}+\frac{10}{13\cdot23}+\cdots+\frac{10}{53\cdot63}\right)\)

\(=\frac{7}{10}\left(\frac13-\frac{1}{13}+\frac{1}{13}-\frac{1}{23}+\cdots+\frac{1}{53}-\frac{1}{63}\right)\)

\(=\frac{7}{10}\left(\frac13-\frac{1}{63}\right)=\frac{7}{10}\cdot\frac{20}{63}=\frac29\)

=>Chọn D

Ta có : A = -(a - b + c) - (-a - b - c)

= -a + b - c + a - b + c

= 0

A = (-a - b + c) - (-a - b - c)

= -a - b + c + a + b + c

= (-a + a) + (-b + b) + (c + c)

= 2c

Vậy A = 2c.

A)=-8+8=0

B)=-221

2) chua lam duoc

cho minh nha

cho minh nha

\(\frac{5.4^{15}.9^9-4.3^{20}.8^9}{5.2^9.6^{19}-7.2^{29}.27^6}\)

\(=\frac{5.2^{30}.3^{18}-3^{20}.2^{29}}{5.2^9.3^{19}.2^{19}-7.2^{29}.3^{18}}\)

\(=\frac{5.2^{30}.3^{18}-3^{20}.2^{29}}{5.2^{28}.3^{19}-7.2^{29}.3^{18}}\)

\(=\frac{3^{18}.2^{29}.\left(5+1-9+2\right)}{2^{28}.3^{18}.\left(5+3-7-2\right)}\)

\(=\frac{2.\left(-1\right)}{-1}=2\)

Vậy đáp án C đúng.

đưa máy tính mà tính chứ