Question

a) 64^x : 16^x = 256

b) -2401/7^x = -7

c) 625/ (-5)^x = 25

Answer 1

a: \(64^x:16^x=256\)

=>\(\left(\dfrac{64}{16}\right)^x=256\)

=>\(4^x=256=4^4\)

=>x=4

b: \(-\dfrac{2401}{7^x}=-7\)

=>\(7^x=\dfrac{2401}{7}=343=7^3\)

=>x=3

c: \(\dfrac{625}{\left(-5\right)^x}=25\)

=>\(\left(-5\right)^x=\dfrac{625}{25}=25\)

=>\(\left(-5\right)^x=\left(-5\right)^2\)

=>x=2

Answer 2

\(a,64^x:16^x=256\)
\(\left(\dfrac{64}{16}\right)^x=4^4\)
\(4^x=4^4\)
\(x=4\)
Vậy \(x=4\)
\(b,\dfrac{-2401}{7^x}=-7\)
\(7^x=\left(-2401\right):\left(-7\right)\)
\(7^x=343\)
\(7^x=7^3\)
\(x=3\)
Vậy \(x=3\)
\(c,\dfrac{625}{\left(-5\right)^x}=25\)
\(\left(-5\right)^x=625:25\)
\(\left(-5\right)^x=25\)
\(\left(-5\right)^x=\left(-5\right)^2\)
\(x=2\)
Vậy \(x=2\)