(5.5-3√2)a^2+(9-3√2)a+3.5=0有一解为a=-1,那另一解为多少?

题目

(5.5-3√2)a^2+(9-3√2)a+3.5=0有一解为a=-1,那另一解为多少?
算出来两解为√[（9-3√2）^2+/-4*(5.5-3√2)*3.5]/[2*(5.5-3√2)].

答案

韦达定理
x1x2=3.5/(5.5-3√2)
=3.5(5.5+3√2)/(5.5²-3²*2)
=3.5(5.5+3√2)/3.5²
=(5.5+3√2)/3.5
x1=-1
所以另一解是-(5.5+3√2)/3.5