Question

知x平方-ax-2=0的两个根x1,x2,x1-x2的绝对值＝4.则x1+x2=?,x1乘x2=?,知x1-x2的绝对值

Answer 1

x1+x2=a

x1*x2=-2

/x1-x2/=4

(x1-x2)^2=16

(x1+x2)^2-4x1*x2=16

a^2 +8=16

a^2=8

a=±2√2

(/x1-x2/)^2=(x1-x2)^2=16