Question

mọi người giúp mình với...

a/(1+3x)^4=256

\(\dfrac{\text{A= 3^15.29+3^15.88}}{3^{13}.81}\)

Answer 1

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Answer 2

a, \(\left(1+3x\right)^4=256\)

\(\left(1+3x\right)^4=4^4\)

\(\Rightarrow1+3x=4\)

\(\Rightarrow3x=3\)

\(x=1\)

b, \(A=\dfrac{3^{15}.29+3^{15}.88}{3^{13}.81}\)

\(A=\dfrac{3^{15}\left(29+88\right)}{3^{13}.81}\)

\(A=\dfrac{3^{15}.117}{3^{13}.3^4}\)

\(A=\dfrac{3^{15}.3^2.13}{3^{17}}\)

\(A=\dfrac{3^{17}.13}{3^{17}}=13\)

Answer 3

\(\left(1+3x\right)^4=256\)

\(\Leftrightarrow\left(1+3x\right)^4=\left(\pm4\right)^4\)

\(\Leftrightarrow1+3x=4\Rightarrow3x=3\Rightarrow x=1\)

\(\Leftrightarrow1+3x=-4\Rightarrow3x=-5\Rightarrow x=\dfrac{-5}{3}\)

Answer 4

\(A=\dfrac{3^{15}.29+3^{15}.88}{3^{13}.81}\)

\(A=\dfrac{3^{15}\left(29+88\right)}{3^{13}.81}\)

\(A=\dfrac{3^{15}.117}{3^{13}.81}\)

\(A=\dfrac{3^{15}.3^2.13}{3^{13}.3^4}\)

\(A=\dfrac{3^{17}.13}{3^{17}}=13\)