Question

   giúp mình với 

 a)  (2/3)^5 .  (2/3)^x = (2/3)^8

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

 

cảm ơn 

Answer 1

a: \(\left(\dfrac{2}{3}\right)^5\cdot\left(\dfrac{2}{3}\right)^x=\left(\dfrac{2}{3}\right)^8\)

=>\(\left(\dfrac{2}{3}\right)^{x+5}=\left(\dfrac{2}{3}\right)^8\)

=>x+5=8

=>x=8-5=3

b: \(\left(-\dfrac{3}{4}\right)^x:\left(-\dfrac{3}{4}\right)^7=\left(-\dfrac{3}{4}\right)^2\)

=>\(\left(-\dfrac{3}{4}\right)^{x-7}=\left(-\dfrac{3}{4}\right)^2\)

=>x-7=2

=>x=2+7=9

Answer 2

`(2/3)^5 . (2/3)^x = (2/3)^8`

`=> (2/3)^(x + 5) = (2/3)^8`

`=> x + 5 = 8`

`=> x = 3`

`(-3/4)^x : (-3/4)&7  (-3/4)^2`

`=>(-3/4)^(x - 7) = (-3/4)^2`

`=> x - 7 = 2`

`=> x = 9`