Question

so sánh:

A= 3³² - 1

B= 2(3² +1 )(3⁴ + 1)(3⁸ + 1)(3¹⁶+1)

Answer 1

\(B=2\left(3^2+1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)=\dfrac{8\left(3^2+1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)}{4}=\dfrac{\left(3^2-1\right)\left(3^2+1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)}{4}=\dfrac{\left(3^4-1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)}{4}=\dfrac{\left(3^8-1\right)\left(3^8+1\right)\left(3^{16}+1\right)}{4}=\dfrac{\left(3^{16}-1\right)\left(3^{16}+1\right)}{4}=\dfrac{3^{32}-1}{4}\)

=>A>B

Answer 2

Ta có:







Suy ra