Tìm x, biết:
Bài 4. Tìm x, biết:
a) $x/(\frac{-1}{3})^{3}=\frac{-1}{3}$
b) $x\times (\frac{-3}{7})^{5}=(\frac{-3}{7})^{7}$
c) $(\frac{-2}{3})^{12}/x=(\frac{-2}{3})^{9}$
d) $(x+\frac{1}{3})^{2}=\frac{1}{25}$
a) $x/(\frac{-1}{3})^{3}=\frac{-1}{3}$ suy ra $x=(\frac{-1}{3})^{4}=\frac{1}{81}$
b) $x\times (\frac{-3}{7})^{5}=(\frac{-3}{7})^{7}$ suy ra $x=(\frac{-3}{7})^{2}=\frac{9}{49}$
c) $(\frac{-2}{3})^{12}/x=(\frac{-2}{3})^{9}$ suy ra $x=(\frac{-2}{3})^{12}/(\frac{-2}{3})^{9}=(\frac{-2}{3})^{3}$ nên $x = \frac{-8}{27}$
d) $(x+\frac{1}{3})^{2}=\frac{1}{25}$ suy ra $(x+\frac{1}{3})^{2}=(\frac{1}{5})^{2}$
Vậy: $x +\frac{1}{3}=\frac{1}{5}$ hay $x+\frac{1}{3}=\frac{-1}{5}$. Do đó $x=\frac{-2}{15}$ hay $x=\frac{-8}{15}$
Bình luận