We can't help you without knowing what YOU know about this problem yourself. What is the definition of "p-summable sequences"? What is the definition of "inner product space"? What is the definition of "inner product"?
We can't help you without knowing what YOU know about this problem yourself. What is the definition of "p-summable sequences"? What is the definition of "inner product space"? What is the definition of "inner product"?