Question

一元二次方程，急求回答！！！

①(X＋1)(X－4)=0
②X²－2X－4=0﹙公式法﹚
③4X²－3=4X﹙配方法﹚
④﹙X＋1﹚﹙X＋8﹚=﹣12
⑤﹙2X－1﹚²＋3﹙2X－1﹚＋2=0

Answer 1

1）x1=-1 x2=4
2) x1,2=(2±√(4+16))/2=1±√5 x1=1+√5 x2=1-√5
3)4x²-4x=3 x²-x=3/4 x²-2*(1/2)x+(1/2)²=3/4+1/4 (x-1/2)²=1 x-1/2=±1
x1=3/2 x2=-1/2
4)x²+9x+20=0 (x+4)(x+5)=0 x1=-4 x2=-5
5) [(2x-1)+2][(2x-1)+1]=0 (2x-1)'=-2 (2x-1)"=-1 x1=-1/2 x2=0

Answer 2

楼上正解