Tính:
a) \(\dfrac{5^{15}.7^{14}}{5^{16}.7^{16}}\)=\(\dfrac{1}{5.7^2}\)=\(\dfrac{1}{5.49}\)=\(\dfrac{1}{245}\)
b)\(\dfrac{3^{12}.7^{13}}{3^{10}.7^{11}}\)=\(\dfrac{3^2.7^2}{1}\)=\(\dfrac{9.49}{1}\)=\(\dfrac{441}{1}\)
c)\(\dfrac{8^{10}.3^{15}}{9^8.2^{83}}\)=\(\dfrac{\left(2^3\right)^{10}.3^{15}}{\left(3^2\right)^8.2^{83}}\)=\(\dfrac{2^{30}.3^{15}}{3^{16}.2^{83}}\)=\(\dfrac{1}{3.2^{53}}\)= bài c) hình như bị lỗi rồi
não mình úng nước rồi, không biết làm d), e) và f)
Tìm x:
a) x - \(\dfrac{1}{2}\)=\(\dfrac{3}{4}\)
x =\(\dfrac{3}{4}\)+\(\dfrac{1}{2}\)
x = \(\dfrac{3}{4}+\dfrac{2}{4}\)
x = \(\dfrac{5}{4}\)
b)\(\dfrac{1}{7}\) - x = \(-\dfrac{5}{6}\)
- x = \(-\dfrac{5}{6}\)\(-\dfrac{1}{7}\)
- x = \(-\dfrac{35}{42}-\dfrac{6}{42}\)
- x = \(-\dfrac{41}{42}\)
x = \(\dfrac{41}{42}\)
c) - x + \(\dfrac{1}{2}\) = \(-\dfrac{10}{11}\)
-x = \(-\dfrac{10}{11}-\dfrac{1}{2}\)
- x = \(-\dfrac{20}{22}-\dfrac{11}{22}\)
- x = \(-\dfrac{31}{22}\)
x = \(\dfrac{31}{22}\)
d) - x \(-\dfrac{3}{4}\) = \(-\dfrac{7}{5}\)
- x = \(-\dfrac{7}{5}+\dfrac{3}{4}\)
- x = \(-\dfrac{28}{20}+\dfrac{15}{20}\)
- x = \(-\dfrac{13}{20}\)
x = \(\dfrac{13}{20}\)
