(1)x2+12x=0; (2)4x2-1=0; (3)x2=7x (4)x2-4x-21=0; (5)(x-1)(x+3)=12;(6)3x2+2x-1=0; (7)10x2-x-3=0;\x05\x05\x05\x05\x05(8)(x-1)2-4(x-1)-21=0(9)x2-4x+3=0;\x05\x05\x05\x05\x05(10)(x-2)2
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![(1)x2+12x=0; (2)4x2-1=0; (3)x2=7x (4)x2-4x-21=0; (5)(x-1)(x+3)=12;(6)3x2+2x-1=0; (7)10x2-x-3=0;\x05\x05\x05\x05\x05(8)(x-1)2-4(x-1)-21=0(9)x2-4x+3=0;\x05\x05\x05\x05\x05(10)(x-2)2](/uploads/image/z/2545806-30-6.jpg?t=%281%29x2%EF%BC%8B12x%EF%BC%9D0%EF%BC%9B+%282%294x2%EF%BC%8D1%EF%BC%9D0%EF%BC%9B+%283%29x2%EF%BC%9D7x+%284%29x2%EF%BC%8D4x%EF%BC%8D21%EF%BC%9D0%EF%BC%9B+%285%29%28x%EF%BC%8D1%29%28x%EF%BC%8B3%29%EF%BC%9D12%EF%BC%9B%286%293x2%EF%BC%8B2x%EF%BC%8D1%EF%BC%9D0%EF%BC%9B%E3%80%80%E3%80%80%287%2910x2%EF%BC%8Dx%EF%BC%8D3%EF%BC%9D0%EF%BC%9B%5Cx05%5Cx05%5Cx05%5Cx05%5Cx05%288%29%28x%EF%BC%8D1%292%EF%BC%8D4%28x%EF%BC%8D1%29%EF%BC%8D21%EF%BC%9D0%289%29x2%EF%BC%8D4x%EF%BC%8B3%EF%BC%9D0%EF%BC%9B%5Cx05%5Cx05%5Cx05%5Cx05%5Cx05%2810%29%28x%EF%BC%8D2%292)
(1)x2+12x=0; (2)4x2-1=0; (3)x2=7x (4)x2-4x-21=0; (5)(x-1)(x+3)=12;(6)3x2+2x-1=0; (7)10x2-x-3=0;\x05\x05\x05\x05\x05(8)(x-1)2-4(x-1)-21=0(9)x2-4x+3=0;\x05\x05\x05\x05\x05(10)(x-2)2
(1)x2+12x=0; (2)4x2-1=0; (3)x2=7x (4)x2-4x-21=0; (5)(x-1)(x+3)=12;
(6)3x2+2x-1=0;
(7)10x2-x-3=0;\x05\x05\x05\x05\x05(8)(x-1)2-4(x-1)-21=0
(9)x2-4x+3=0;\x05\x05\x05\x05\x05(10)(x-2)2=256;\x05\x05\x05\x05\x05\x05(11)x2-3x+1=0;
(12)x2-2x-3=0;\x05\x05\x05\x05\x05(13)(2t+3)2=3(2t+3);
(14) (3-y)2+y2=9;
(1)x2+12x=0; (2)4x2-1=0; (3)x2=7x (4)x2-4x-21=0; (5)(x-1)(x+3)=12;(6)3x2+2x-1=0; (7)10x2-x-3=0;\x05\x05\x05\x05\x05(8)(x-1)2-4(x-1)-21=0(9)x2-4x+3=0;\x05\x05\x05\x05\x05(10)(x-2)2
直接写答案?
⑴x²+12x=0
x(x+12)=0
x=0或x=-12
⑵4x²-1=0
4x²=1
x²=1/4
x=±1/2
⑶x²=7x
x²-7x=0
x(x-7)=0
x=0或x=7
⑷x²-4x-21=0
(x-7)(x+3)=0
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⑴x²+12x=0
x(x+12)=0
x=0或x=-12
⑵4x²-1=0
4x²=1
x²=1/4
x=±1/2
⑶x²=7x
x²-7x=0
x(x-7)=0
x=0或x=7
⑷x²-4x-21=0
(x-7)(x+3)=0
x=7或x=-3
⑸(x-1)(x+3)=12
x²+2x-3-12=0
x²+2x-15=0
(x+5)(x-3)=0
x=-5或x=3
⑹3x²+2x-1=0
(3x-1)(x+1)=0
x=1/3或x=-1
⑺10x²-x-3=0
(2x+1)(5x-3)=0
x=-1/2或x=3/5
⑻(x-1)²-4(x-1)-21=0
[(x-1)-7][(x-1)+3]=0
(x-8)(x+2)=0
x=8或x=-2
⑼x²-4x+3=0
(x-1)(x-3)=0
x=1或x=3
⑽(x-2)²=256
x-2=±16
x-2=16或x-2=-16
x=18或x=-14
⑾x²-3x+1=0
求根公式:△=b²-4ac=(-3)²-4×1×1=5
x=[-(-3)±√5]/2=(3±√5)/2
⑿x²-2x-3=0
(x-3)(x+1)=0
x=3或x=-1
⒀(2t+3)²=3(2t+3)
(2t+3)²-3(2t+3)=0
(2t+3)[(2t+3)-3]=0
2t(2t+3)=0
t=0或t=-3/2
⒁(3-y)²+y²=9
9-6y+y²+y²=9
2y²-6y=0
2y(y-3)=0
y=0或y=3
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