x²+4x-9=2x-11
x²+2x+2=0
x²+2x+1+1=0
(x+1)^2=-1
方程无实数解
x²-X-4/7=0
x²-X+(1/2)^2-(1/2)^2-4/7=0
(x - 1/2)^2=23/28
x=1/2 ±√23/28
x=(7 ±√161)/14
X²-x-4/3=0
X²-x+(1/2)^2-(1/2)^2-4/3=0
(x-1/2)^2=19/12
x=(3 ±√57)/6
4x²-x-9=0
用公式法解得
x=(1±√1+4*4*9)/2*4
x=(1±√145)/8