Question

[Phạm Chí Bảo]

a)Tìm các số nguyên x,y biết (x-3)(y-3) = 9

b)So sánh hai phân số A = 10^19 + 1/10^20 + 1 ; B = 10^20 + 1/10^21 + 1

Answer 1

[Kuroba Kaito]

a) (x - 3)(y - 3) = 9 = 1.9 = 3.3

Lập bảng:

x - 3	1	-1	3	-3	9	-9
y - 3	9	-9	3	-3	1	-1
x	4	2	6	0	12	-3
y	12	-6	6	0	4	2

Vậy ...

Answer 2

[Kuroba Kaito]

b) A = \(\frac{10^{19}+1}{10^{20}+1}\) => 10A = \(\frac{10^{20}+10}{10^{20}+1}=1+\frac{9}{10^{20}+1}\)

B = \(\frac{10^{20}+1}{10^{21}+1}\) => 10B = \(\frac{10^{21}+10}{10^{21}+1}=1+\frac{9}{10^{21}+1}\)

Do \(10^{20}+1< 10^{21}+1\) => \(\frac{9}{10^{20}+1}>\frac{9}{10^{21}+1}\) => 10A > 10B => A > B