Tìm x thuộc n a) (2/3)^5 . (2/3)^x = (2/3)^8 b) (-3/4)^x : (-3/4)^7 = (-3/4)^2

2 bình luận về “Tìm x thuộc n a) (2/3)^5 . (2/3)^x = (2/3)^8 b) (-3/4)^x : (-3/4)^7 = (-3/4)^2”

1. a) (2/3)^5 . (2/3)^x = (2/3)^8

   (2/3)^x = (2/3)^8 : (2/3)^5

   (2/3)^x = (2/3)^3

   => x = 3

   ——-

   b) (-3/4)^x : (-3/4)^7 = (-3/4)^2

   (-3/4)^x = (-3/4)^2 . (-3/4)^7

   (-3/4)^x = (-3/4)^9

   => x = 9

   Trả lời
2. a)

   ( $\frac{2}{3}{)}^5$ . ( $\frac{2}{3}{)}^x$ = ( $\frac{2}{3}{)}^8$

   ⇔ ( $\frac{2}{3}{)}^{5+x}$  = ( $\frac{2}{3}{)}^8$

   ⇔ 5 + x = 8

   ⇔ x = 3

   b)

   ( $\frac{-3}{4}{)}^x$ . ( $\frac{-3}{4}{)}^7$ = ( $\frac{-3}{4}{)}^2$

   ⇔ ( $\frac{-3}{4}{)}^{x-7}$  = ( $\frac{-3}{4}{)}^2$

   ⇔ x – 7 = 2

   ⇔ x = 9

   Trả lời