đến 1/5 là xuống phần mẫu số nhé

Ta có: \(99^{99}-\left\lbrace1,\left(3\right)-\left\lbrack5\cdot2^3-\left(-7\right)^2+\frac13+99^9\cdot\left(27^4-81^3-99^{90}\right)\right\rbrack\right\rbrace\)

\(=99^{99}-\left\lbrace\frac43-\left\lbrack5\cdot8-49+\frac13+99^9\cdot\left(\left(3^3\right)^4-\left(3^4\right)^3-99^{90}\right)\right\rbrack\right\rbrace\)

\(=99^{99}-\left\lbrace\frac43-\left\lbrack40-49+\frac13+99^9\cdot\left(3^{12}-3^{12}-99^{90}\right)\right\rbrack\right\rbrace\)

\(=99^{99}-\left\lbrace\frac43-\left\lbrack-9+\frac13+99^9\cdot\left(-99^{90}\right)\right\rbrack\right\rbrace\)

\(=99^{99}-\left\lbrace\frac43-\left\lbrack-\frac{26}{3}-99^{99}\right\rbrack\right\rbrace=99^{99}-\frac43+\left\lbrack-\frac{26}{3}-99^{99}\right\rbrack\)

\(=-\frac43-\frac{26}{3}\)

\(=-\frac{30}{3}=-10\)

thank

12/5.(-15/16).(-1/9)

= (-9/4).(-1/9)

=1/4

\(B=\frac{\left(\frac{1}{5}-\frac{2}{7}\right).\frac{3}{4}-\frac{3}{4}.\left(\frac{1}{3}-\frac{2}{7}\right)}{\frac{1}{5}.\frac{2}{7}-\frac{1}{3}.\left(\frac{2}{7}+\frac{3}{9}\right)+\frac{3}{9}.\frac{1}{5}}\)

\(B=\frac{\frac{3}{4}.\left(\frac{1}{5}-\frac{2}{7}-\frac{1}{3}+\frac{2}{7}\right)}{\frac{1}{5}.\frac{2}{7}-\frac{1}{3}.\frac{2}{7}-\frac{1}{3}.\frac{1}{3}+\frac{1}{3}.\frac{1}{5}}\)

\(B=\frac{\frac{3}{4}.\left(\frac{1}{5}-\frac{1}{3}\right)}{\frac{2}{7}.\left(\frac{1}{5}-\frac{1}{3}\right)-\frac{1}{3}.\left(\frac{1}{3}-\frac{1}{5}\right)}\)

\(B=\frac{\frac{3}{4}.\left(\frac{1}{5}-\frac{1}{3}\right)}{\frac{2}{7}.\left(\frac{1}{5}-\frac{1}{3}\right)+\frac{1}{3}.\left(\frac{1}{5}-\frac{1}{3}\right)}\)

\(B=\frac{\frac{3}{4}.\left(\frac{1}{5}-\frac{1}{3}\right)}{\left(\frac{2}{7}+\frac{1}{3}\right).\left(\frac{1}{5}-\frac{1}{3}\right)}\)

\(B=\frac{\frac{3}{4}.\left(\frac{1}{5}-\frac{1}{3}\right)}{\frac{13}{21}.\left(\frac{1}{5}-\frac{1}{3}\right)}=\frac{\frac{3}{4}}{\frac{13}{21}}=\frac{3}{4}:\frac{13}{21}=\frac{63}{52}\)

a. Ta có : 2,5 < 5,2 => 2,5³ < 5,2³

b. Ta có : 4⁵ = 1024      ;        5⁴ = 625

Vì 1024 > 625 => 4⁵ > 5⁴

\(a.2.5^3va5.2^3\)

\(2.5^3=2.125=250;5.2^3=5.8=40\)

Vì \(250>40\)

\(\Rightarrow2.5^3>5.2^3\)

\(b.4^5va5^4\)

\(4^5=1024;5^4=625\)

Vì \(1024>625\)

\(\Rightarrow4^5>5^4\)

\(c.2^8va2.5^3\)

\(2^8=256;2.5^3=2.125=250\)

Vì \(256>250\)

\(\Rightarrow2^8>2.5^3\)

2.Tìm x:

\(a.2^n+4.2^n=5.2^5\)

  \(2^n\left(1+4\right)=5.32\) 

                \(2^n.5=160\)

                    \(2^n=160:5\)

                    \(2^n=32\)

                    \(2^n=2^5\)

                \(\Rightarrow n=5\)

\(b.3^4.3^n:9=3^7\)

  \(3^4.3^n:3^2=3^7\)

        \(3^4.3^n=3^7.3^2\)

        \(3^4.3^n=3^{7+2}\)

        \(3^4.3^n=3^9\)

              \(3^n=3^9:3^4\)

              \(3^n=3^{9-4}\)

              \(3^n=3^5\)

          \(\Rightarrow n=5\)

\(c.6.2^n+3.2^n=9.2^n\)

     \(2^n\left(6+3\right)=9.2^n\)

                   \(2^n.9=9.2^n\)

                  \(\Rightarrow2^n=9:9\)

                  \(\Rightarrow2^n=1\)

                  \(\Rightarrow2^n=2^0\)

                    \(\Rightarrow n=0\)

Chúc bạn học tốt!