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
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`(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`
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