Tính giá trị biểu thức sau:
a)\(\frac{1^2}{1.2}\)x \(\frac{2^2}{2.3}\)x\(\frac{3^2}{3.4}\)x\(\frac{4^2}{4.5}\)x\(\frac{5^2}{5.6}\)
b)\(\frac{2^2}{1.3}\)x\(\frac{3^2}{2.4}\)x\(\frac{4^2}{3.5}\)x\(\frac{5^2}{4.6}\)x\(\frac{6^2}{5.7}\)
c)(\(1+\frac{1}{2}\))(\(1+\frac{1}{3}\))(\(1+\frac{1}{4}\))(1+\(\frac{1}{5}\))