Question

因式分解法解一元二次方程

用分解因式解一元二次方程
4（x-3)的方=x的方—9

Answer 1

一楼的方法正确！但是解错了哦
4（x-3)的方=x的方—9

(4X-12)(X-3)=(X-3)(X+3)

(4X-12)(X-3)-(X-3)(X+3)=0

(4X-12-X-3)(X-3)=0

（3X-15)(X-3)=0

3(X-5)(X-3)=0
所以 解应该是X=3 或X=5

Answer 2

4(x-3)^2=x^2-9
4(x-3)^2-(x^2-9)=0
4(x-3)^2-(x-3)(x+3)=0
(x-3)[4(x-3)-(x+3)]=0
(x-3)[4x-12-x-3]=0
(x-3)(3x-15)=0
(x-3)(x-5)=0
x=3或x=5

Answer 3

4（x-3)的方=x的方—9

(4X-12)(X-3)=(X-3)(X+3)

(4X-12)(X-3)-(X-3)(X+3)=0

(4X-12-X-3)(X-3)=0
(3X-9)(X-3)=0

3(X-3)^2=0

X=3