降次求方程的解:(1)x^2-4x+4=0 (2)5x^2-15x=0 (3)x^2-5x+6=0 (4) 2x^2-7x+3=0

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降次求方程的解:(1)x^2-4x+4=0 (2)5x^2-15x=0 (3)x^2-5x+6=0 (4) 2x^2-7x+3=0

降次求方程的解:(1)x^2-4x+4=0 (2)5x^2-15x=0 (3)x^2-5x+6=0 (4) 2x^2-7x+3=0
降次求方程的解:(1)x^2-4x+4=0 (2)5x^2-15x=0 (3)x^2-5x+6=0 (4) 2x^2-7x+3=0

降次求方程的解:(1)x^2-4x+4=0 (2)5x^2-15x=0 (3)x^2-5x+6=0 (4) 2x^2-7x+3=0
(1)x^2-4x+4=0
(x-2) ^2=0(完全平方公式),x=2
(2)5x^2-15x=0
5x(x-3)=0(提取公因式)
x=0或x=3
(3)x^2-5x+6=0
(x-2)(x-3)=0(因式分解)
x=2或x=3
(4) 2x^2-7x+3=0
(2x-1)(x-3)=0 (因式分解)
x=0.5或x=3

1, x^2-4x+4=0
(x-2)^2=0
x=2
2, 5x^2-15x=0
5(x^2-3x+9/4)=5*(9/4)
(x-3/2)^2=9/4
x-3/2=3/2或x-3/2=-3/2
所以x=3或x=0
3,x^2-5x+6=0
x^2-5x+2...

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1, x^2-4x+4=0
(x-2)^2=0
x=2
2, 5x^2-15x=0
5(x^2-3x+9/4)=5*(9/4)
(x-3/2)^2=9/4
x-3/2=3/2或x-3/2=-3/2
所以x=3或x=0
3,x^2-5x+6=0
x^2-5x+25/4=1/4
(x-5/2)^2=1/4
x-5/2=1/2或x-5/2=-1/2
所以x=3或x=2
4, 2x^2-7x+3=0
2(x^2-7x/2+49/16)=25/8
(x-7/4)^2=25/16
x-7/4=5/4或x-7/4=-5/4
所以x=3或x=1/2

收起

x²-4x+4>0
(x-2)²>0
因为平方数大于等于0
所以只要(x-2)²≠0
x-2≠0
x≠2
5x^2-15x=0 可化为5*x*x=15*x X=3或0
X^2-5X+6=0
(x-2)(x-3)=0
x1=2, x2=3
2x^2-7x+3
=(2x-1)(x-3)