Question

若非零向量a,b满足绝对值a=√7+1,绝对值b=√7-1,且绝对值a-b=4,则绝对值a+b=?

Answer 1

| a-b| ^2 = a^2 + b^2 - 2ab= 16

|a|^2= 8 + 2根号(7)

|b| ^2 = 8 - 2根号(7)

2ab= 0

| a+b| ^2 = a^2 +b^2 +2ab =16

|a+b|=4