已知X1,X2是方程X²+3X-5=0的两根,则 (X1+1)(X2+2)=?X1²+X2²=?(X_数学解答

已知X1,X2是方程X²+3X-5=0的两根,则 (X1+1)(X2+2)=?X1²+X2²=?(X1-X2)²=?

人气：344 ℃　时间：2020-01-29 22:31:36

解答

(x1+1)(x2+1)
=x1x2+x1+x2+1
=-5-3+1
=-7
x1^2+x2^2
=(x1+x2)^2-2x1x2
=9-2*(-5)
=19
(x1-x2)^2
=(x1+x2)^2-4x1x2
=9-4*(-5)
=29