Question

so sánh -11 trên 3^7 nhân 7^3 và -78 trên 3^7 nhân 7^4

Answer 1

Ta có:

\(\dfrac{-11}{3^7.7^3}=\dfrac{-11}{\dfrac{3^7.7^4.1}{7}}=-\dfrac{77}{3^7.7^4}=\dfrac{-78+1}{3^7.7^4}=\dfrac{-78}{3^7.7^4}+\dfrac{1}{3^7.7^4}\)

Do \(3^7.7^4>3^4.7^4\)

\(\text{⇒}\dfrac{78}{3^7.7^4}< \dfrac{78}{3^4.7^4}\text{⇒}\dfrac{-78}{3^7.7^4}>\dfrac{-78}{3^4.7^4}\text{⇒}\dfrac{-78}{3^7.7^4}+\dfrac{1}{3^7.7^4}>\dfrac{-78}{3^4.7^4}\text{⇒}\dfrac{-11}{3^7.7^3}>\dfrac{-78}{3^4.7^4}\)