求这四道题的解题过程 10
2个回答
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(1) x² +10x + 9 = 0
(x + 1)(x + 9) = 0
x = -1 或 x = -9
(2) x² - x - 7/4 = 0
4x² - 4x - 7 = 0
将系数代入求根公式得:
x = 1/2 ± √2
(3) x² + 4x - 9 = 2x - 11
x² + 2x +2 = 0
(x + 1)² + 1 = 0
无解
(4) x(x + 4) = 8x + 12
x² - 4x - 12 = 0
(x + 2)(x - 6) = 0
x = -2 或 x = -6
(x + 1)(x + 9) = 0
x = -1 或 x = -9
(2) x² - x - 7/4 = 0
4x² - 4x - 7 = 0
将系数代入求根公式得:
x = 1/2 ± √2
(3) x² + 4x - 9 = 2x - 11
x² + 2x +2 = 0
(x + 1)² + 1 = 0
无解
(4) x(x + 4) = 8x + 12
x² - 4x - 12 = 0
(x + 2)(x - 6) = 0
x = -2 或 x = -6
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解:
(1)x²+10x+9=0
(x+1)(x+9)=0
x1=-1,x2=-9
(2)x²-x-(7/4)=0
x²-x+(1/4)=2
[x-(1/2)]²=2
x-(1/2)=±√2
x1=(1/2)-√2,x2=(1/2)+√2
(3)x²+4x-9=2x-11
x²+2x+2=0
△=4-8=-4<0
此方程无实根
(4)x(x+4)=8x+12
x²-4x-12=0
(x-6)(x+2)=0
x1=6,x2=-2
(1)x²+10x+9=0
(x+1)(x+9)=0
x1=-1,x2=-9
(2)x²-x-(7/4)=0
x²-x+(1/4)=2
[x-(1/2)]²=2
x-(1/2)=±√2
x1=(1/2)-√2,x2=(1/2)+√2
(3)x²+4x-9=2x-11
x²+2x+2=0
△=4-8=-4<0
此方程无实根
(4)x(x+4)=8x+12
x²-4x-12=0
(x-6)(x+2)=0
x1=6,x2=-2
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