So sánh A=(〖19〗^30+5)/(〖19〗^31+5) và B=(〖19〗^31+5)/(〖19〗^32+5) 28/07/2021 Bởi Savannah So sánh A=(〖19〗^30+5)/(〖19〗^31+5) và B=(〖19〗^31+5)/(〖19〗^32+5)
A=19^30+5/19^31+5 ⇔19A=19^31+5+90/19^31+5 ⇔19A=1+ 90/19^31 +5 B=19^31+5/19^32+5 ⇔19B=19^32+5+90/19^32+5⇔19B=1+ 90/19^32 +5 vì 90/19^31 > 90/19^32 ⇒ A>B xin ctlhn Bình luận
Ta có: $A = \dfrac{19^{30} + 5}{19^{31}+5}$ $⇔19A = \dfrac{19^{31} + 95}{19^{31} + 5}$ $⇔ 19A = \dfrac{19^{31} + 5 + 90}{19^{31} + 5}$ $⇔ 19A = 1 + \dfrac{90}{19^{31} + 5}$ $B = \dfrac{19^{31} + 5}{19^{32}+5}$ $⇔19B = \dfrac{19^{32} + 95}{19^{32} + 5}$ $⇔ 19B = \dfrac{19^{32} + 5 + 90}{19^{32} + 5}$ $⇔ 19B = 1 + \dfrac{90}{19^{32} + 5}$ Vì : $\dfrac{90}{19^{31} + 5} > \dfrac{90}{19^{32} + 5}$ $→ A > B$. Bình luận
A=19^30+5/19^31+5
⇔19A=19^31+5+90/19^31+5
⇔19A=1+ 90/19^31 +5
B=19^31+5/19^32+5
⇔19B=19^32+5+90/19^32+5
⇔19B=1+ 90/19^32 +5
vì 90/19^31 > 90/19^32
⇒ A>B
xin ctlhn
Ta có:
$A = \dfrac{19^{30} + 5}{19^{31}+5}$
$⇔19A = \dfrac{19^{31} + 95}{19^{31} + 5}$
$⇔ 19A = \dfrac{19^{31} + 5 + 90}{19^{31} + 5}$
$⇔ 19A = 1 + \dfrac{90}{19^{31} + 5}$
$B = \dfrac{19^{31} + 5}{19^{32}+5}$
$⇔19B = \dfrac{19^{32} + 95}{19^{32} + 5}$
$⇔ 19B = \dfrac{19^{32} + 5 + 90}{19^{32} + 5}$
$⇔ 19B = 1 + \dfrac{90}{19^{32} + 5}$
Vì : $\dfrac{90}{19^{31} + 5} > \dfrac{90}{19^{32} + 5}$
$→ A > B$.