\(.4.\)
\(.a.\)
\(\left(\frac{1}{2}\right)^{15}.\left(\frac{1}{4}\right)^{20}\)
\(=\left(\frac{1}{2}\right)^{15}.\left[\left(\frac{1}{2}\right)^2\right]^{20}\)
\(=\left(\frac{1}{2}\right)^{15}.\left(\frac{1}{2}\right)^{40}\)
\(=\left(\frac{1}{2}\right)^{15+40}\)
\(=\left(\frac{1}{2}\right)^{55}\)
\(.b.\)
\(\left(\frac{1}{9}\right)^{25}:\left(\frac{1}{3}\right)^{30}\)
\(=\left[\left(\frac{1}{3}\right)^2\right]^{25}:\left(\frac{1}{3}\right)^{30}\)
\(=\left(\frac{1}{3}\right)^{50}:\left(\frac{1}{3}\right)^{30}\)
\(=\left(\frac{1}{3}\right)^{50-30}\)
\(=\left(\frac{1}{3}\right)^{20}\)
\(.c.\)
\(\frac{4^5.9^4-2.6^9}{2^{10}.3^8+6^8.20}\)
\(=\frac{2^{10}.3^8-2.2^9.3^9}{2^{10}.3^8+2^8.3^8.2^2.5}\)
\(=\frac{2^{10}.3^8-2^{10}.3^9}{2^{10}.3^8+2^{10}.3^8.5}\)
\(=\frac{2^{10}.3^8.\left(1-3\right)}{2^{10}.3^8.\left(1+5\right)}\)
\(=\frac{2^{10}.3^8.\left(-2\right)}{2^{10}.3^8.6}\)
\(=\frac{\left(-2\right)}{6}\)
\(=\frac{\left(-1\right)}{3}\)
Bài 4:
a/ \(\left(\frac{1}{2}\right)^{15}\cdot\left(\frac{1}{4}\right)^{20}=\left(\frac{1}{2}\right)^{15}\cdot\left[\left(\frac{1}{2}\right)^2\right]^{20}\)
\(=\left(\frac{1}{2}\right)^{15}\cdot\left(\frac{1}{2}\right)^{40}\)
\(=\left(\frac{1}{2}\right)^{55}\)
b/\(\left(\frac{1}{9}\right)^{25}\div\left(\frac{1}{3}\right)^{30}=\left(\frac{1}{9}\right)^{25}\div\left[\left(\frac{1}{3}\right)^2\right]^{15}\)
\(=\)\(\left(\frac{1}{9}\right)^{25}\div\left(\frac{1}{9}\right)^{15}\)
thiếu chút
\(=\left(\frac{1}{9}\right)^{10}\)
Bài 1 (mình chỉ có thể làm được câu a và c thôi, bởi vì câu b và d mình không thấy được 
, bạn có thể nói câu b và d là gì không?)
Câu a)
\(f\left(7\right)=\frac{7+2}{7-1}=\frac{3}{2}\)
Câu c)
- Mình cho x bằng 4 nhé
\(f\left(4\right)=\frac{4+2}{4-1}=2\)
đang cần gấp help meee