已知x²-5x-4=0,两实数根：x1,x2,求；x1² + x2² + x1·x2=

已知x²-5x-4=0,两实数根：x1,x2,求；x1² + x2² + x1·x2=
已知x²-5x-4=0,两实数根：x1,x2,求；
x1² + x2² + x1·x2=

已知x²-5x-4=0,两实数根：x1,x2,求；x1² + x2² + x1·x2=
已知x²-5x-4=0,两实数根：x1,x2
x1+x2=5,x1x2=-4
x1^2+x2^2+x1x2
=(x1+x2)^2-x1x2
=5^2-(-4)
=29

x1² + x2² + x1·x2=（x1+ x2）² - x1·x2=25+4=29
x1+ x2=5
x1·x2=-4