Lời giải:
Ta có:

\(A-\frac{1}{2}=\frac{3}{2}+(\frac{3}{2})^2+...+(\frac{3}{2})^{2012}\)

\(\frac{3}{2}(A-\frac{1}{2})=(\frac{3}{2})^2+(\frac{3}{2})^3+....+(\frac{3}{2})^{2013}\\ \Rightarrow \frac{3}{2}(A-\frac{1}{2})-(A-\frac{1}{2})=(\frac{3}{2})^{2013}-\frac{3}{2}\)

$\Rightarrow \frac{1}{2}(A-\frac{1}{2})=(\frac{3}{2})^{2013}-\frac{3}{2}$

$A-\frac{1}{2}=2(\frac{3}{2})^{2013}-3$

$A=2(\frac{3}{2})^{2013}-2,5$

$\Rightarrow A-B=2(\frac{3}{2})^{2013}-2,5-(\frac{3}{2})^{2013}:2$

$=\frac{3}{2}(\frac{3}{2})^{2013}-2,5=(\frac{3}{2})^{2014}-2,5$

Đáp án:

A>B

#Châu's ngốc

Chết mình thiếu là tính A-B

\(\frac{3}{2}.A=\frac{3}{4}+\left(\frac{3}{2}\right)^2+\left(\frac{3}{2}\right)^3+...+\left(\frac{3}{2}\right)^{2013}\)

\(\Rightarrow\frac{3}{2}.A-A=\frac{3}{4}+\left(\frac{3}{2}\right)^2+\left(\frac{3}{2}\right)^3+...+\left(\frac{3}{2}\right)^{2013}-\left(\frac{1}{2}+\frac{3}{2}+\left(\frac{3}{2}\right)^2+...+\left(\frac{3}{2}\right)^{2012}\right)\)

\(\Rightarrow\frac{1}{2}.A=\frac{3}{4}+\left(\frac{3}{2}\right)^{2013}-\frac{1}{2}-\frac{3}{2}=\left(\frac{3}{2}\right)^{2013}-\frac{5}{4}\Rightarrow A=2.\left(\frac{3}{2}\right)^{2013}-\frac{5}{2}\)

\(B-A=\frac{1}{2}.\left(\frac{3}{2}\right)^{2013}-2.\left(\frac{3}{2}\right)^{2013}+\frac{5}{2}=-\left(\frac{3}{2}\right)^{2014}+\frac{5}{2}\)

Trần Thị Loan tại sao lại + 5/2?

ngu thế Bụng Mon

Lời giải:

$A-\frac{1}{2}=\frac{3}{2}+(\frac{3}{2})^2+....+(\frac{3}{2})^{2012}$

$\frac{3}{2}(A-\frac{1}{2})=(\frac{3}{2})^2+(\frac{3}{2})^3+....+(\frac{3}{2})^{2013}$

$\Rightarrow \frac{3}{2}(A-\frac{1}{2}) - (A-\frac{1}{2})=(\frac{3}{2})^{2013}-\frac{3}{2}$

$\Rightarrow \frac{1}{2}(A-\frac{1}{2})=(\frac{3}{2})^{2013}-\frac{3}{2}$

$\Rightarrow A=2(\frac{3}{2})^{2013}-\frac{5}{2}$

$\Rightarrow A-B=2(\frac{3}{2})^{2013}-\frac{5}{2}- \frac{1}{2}.(\frac{3}{2})^{2013}$

$\Rightarrow A-B=\frac{3}{2}(\frac{3}{2})^{2013}-\frac{5}{2}=(\frac{3}{2})^{2014}-\frac{5}{2}$