Tính nhanh:

a)\(\left(-\dfrac{1}{2}\right)\)-\(\left(-\dfrac{3}{5}\right)\)+\(\left(-\dfrac{1}{5}\right)\)+\(\dfrac{1}{131}\)-\(\left(-\dfrac{2}{7}\right)\)+\(\dfrac{4}{35}\)-\(\dfrac{7}{18}\)

Cho

\(\dfrac{4^x}{2^{x+y}}=8\) và \(\dfrac{9^{x+y}}{3^{5y}}=243\) (x,y \(\in\)N)

Tính xy

B= \(\left(3-\dfrac{1}{4}+\dfrac{2}{3}\right)\) - \(\left(5+\dfrac{1}{3}-\dfrac{6}{5}\right)\) - \(\left(6-\dfrac{7}{4}+\dfrac{3}{2}\right)\)

Tính giá trị cưa biểu thức có nhiều dấu ngoặc:

A= \(\left(6-\dfrac{2}{3}+\dfrac{1}{3}\right)\) - \(\left(5+\dfrac{5}{7}-\dfrac{3}{2}\right)\) - \(\left(3-\dfrac{7}{3}+\dfrac{5}{2}\right)\)

A = \(\dfrac{1}{1x2}+\dfrac{1}{3x4}+\dfrac{1}{5x6}+-+\dfrac{1}{99x100}\)

CM \(\dfrac{7}{12}< A< \dfrac{5}{6}\)

Tính B=\(\left(1-\dfrac{1}{2}\right)\left(1-\dfrac{1}{3}\right)...\left(1-\dfrac{1}{n+1}\right)\) với \(n\in N\)

Tìm x biết :
a) \(x^2-3=1\)
b) \(2x^3+12=-4\)
c) \(\left(2x-3\right)^2=16\)
d) \(x:\left(\dfrac{-1}{2}\right)^1=\dfrac{-1}{2}\)
h) \(\left(\dfrac{1}{4}-x\right)^2=\dfrac{25}{16}\)
i) \(\left(x+\dfrac{1}{3}\right)^3=\dfrac{-1}{8}\)
k) \(\left(\dfrac{1}{2}-x\right)^2=1\)

Tìm x,y thỏa mãn:

\(\left|x+y-7\right|+\left|x.y-10\right|\le0\)

Rút gọn biểu thức sau:

A= 42.252+32.125/23.52

Chứng minh rằng n3 - 3n2-n+3 chia hết cho 48 với mọi số nguyên lẻ n