解二元一次方程:降次 (1)x^2-4x+1=0. (2)3x^2-3x-6=0. (3)2x^2-4x-2.5=0. (4)(x-1)^2-2(x-1)-3=0 ..(1)x^2-4x+1=0. (2)3x^2-3x-6=0. (3)2x^2-4x-2.5=0. (4)(x-1)^2-2(x-1)-3=0 (5)若某商品成本价为360元,两次降价后为100元,若
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![解二元一次方程:降次 (1)x^2-4x+1=0. (2)3x^2-3x-6=0. (3)2x^2-4x-2.5=0. (4)(x-1)^2-2(x-1)-3=0 ..(1)x^2-4x+1=0. (2)3x^2-3x-6=0. (3)2x^2-4x-2.5=0. (4)(x-1)^2-2(x-1)-3=0 (5)若某商品成本价为360元,两次降价后为100元,若](/uploads/image/z/12537838-46-8.jpg?t=%E8%A7%A3%E4%BA%8C%E5%85%83%E4%B8%80%E6%AC%A1%E6%96%B9%E7%A8%8B%EF%BC%9A%E9%99%8D%E6%AC%A1+%EF%BC%881%EF%BC%89x%5E2-4x%2B1%3D0.+%282%293x%5E2-3x-6%3D0.+%283%292x%5E2-4x-2.5%3D0.+%284%29%28x-1%29%5E2-2%28x-1%29-3%3D0+..%EF%BC%881%EF%BC%89x%5E2-4x%2B1%3D0.+%282%293x%5E2-3x-6%3D0.+%283%292x%5E2-4x-2.5%3D0.+%284%29%28x-1%29%5E2-2%28x-1%29-3%3D0+%EF%BC%885%EF%BC%89%E8%8B%A5%E6%9F%90%E5%95%86%E5%93%81%E6%88%90%E6%9C%AC%E4%BB%B7%E4%B8%BA360%E5%85%83%2C%E4%B8%A4%E6%AC%A1%E9%99%8D%E4%BB%B7%E5%90%8E%E4%B8%BA100%E5%85%83%2C%E8%8B%A5)
解二元一次方程:降次 (1)x^2-4x+1=0. (2)3x^2-3x-6=0. (3)2x^2-4x-2.5=0. (4)(x-1)^2-2(x-1)-3=0 ..(1)x^2-4x+1=0. (2)3x^2-3x-6=0. (3)2x^2-4x-2.5=0. (4)(x-1)^2-2(x-1)-3=0 (5)若某商品成本价为360元,两次降价后为100元,若
解二元一次方程:降次 (1)x^2-4x+1=0. (2)3x^2-3x-6=0. (3)2x^2-4x-2.5=0. (4)(x-1)^2-2(x-1)-3=0 ..
(1)x^2-4x+1=0. (2)3x^2-3x-6=0. (3)2x^2-4x-2.5=0. (4)(x-1)^2-2(x-1)-3=0
(5)若某商品成本价为360元,两次降价后为100元,若每次降价的百分率相同,求此百分率 .
(6)某物体以8m/s的初速度在一光滑平面上做变速运动,其运动路程S(m)与时间t(s)满足s=8t+3t^2,求这一物体前进16m所需要的时间
注:要过程.
解二元一次方程:降次 (1)x^2-4x+1=0. (2)3x^2-3x-6=0. (3)2x^2-4x-2.5=0. (4)(x-1)^2-2(x-1)-3=0 ..(1)x^2-4x+1=0. (2)3x^2-3x-6=0. (3)2x^2-4x-2.5=0. (4)(x-1)^2-2(x-1)-3=0 (5)若某商品成本价为360元,两次降价后为100元,若
(1)x^2-4x+1=0
( x^2-4x+4-4)+1=0
(x-2)^2-4+1=0
(x-2)^2=3
x=2±√3
(2) 3x^2-3x-6=0.
x^2- x-2=0
x^2- x+ 1/4 - 1/4 -2=0
( x - 1/2 )^2 =9/4
x=2 x=-1
(3) 2x^2-4x-2.5=0.
x^2-2x-2.5/2=0.
x^2-2x +1 -1=2.5/2
(x-1)^2=1.25+1=2.25
x=1+ √2.25 x= 1-√2.25
(4) (x-1)^2-2(x-1)-3=0 ..
(x-1)^2-2(x-1) +1 -1 -3=0
{(x-1)-1}^2=4
(x-2)^2=4
x=0 x=4
5.设这个百分比为q.
则 360×q×q=100
q=√10/6 ≈ 5.27 √10 (根10≈3.16)
所以该商场打5.27折
6.由题意得:3t^2+8t=16 t﹥0
t^2+8/3 t=16/3
t^2+8/3 t +16/9 -16/9 =16/3
(t+ 4/3)^2 -16/9 =16/3
t + 4/3= 8/3
t=4/3
全部是用同样的方法去组合 (a±1)^2=a^2±2a+1 的公式
(1)2+√3或2-√3
(2)2或-1
(3)1+√5/2或1-√5/2
(4)0,4
(5)设百分率为x
360(1-x)²=100
x1=5/6,x2=-6/7
(1 x=2±√3
(2) 3x^2-3x-6=0.
x^2- x-2=0
x^2- x+ 1/4 - 1/4 -2=0
( x - 1/2 )^2 =9/4
x=2 x=-1
(3) 2x^2-4x-2.5=0.
x^2-2x-2.5/2=0.
...
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(1 x=2±√3
(2) 3x^2-3x-6=0.
x^2- x-2=0
x^2- x+ 1/4 - 1/4 -2=0
( x - 1/2 )^2 =9/4
x=2 x=-1
(3) 2x^2-4x-2.5=0.
x^2-2x-2.5/2=0.
x^2-2x +1 -1=2.5/2
(x-1)^2=1.25+1=2.25
x=1+ √2.25 x= 1-√2.25
(4) (x-1)^2-2(x-1)-3=0 ..
(x-1)^2-2(x-1) +1 -1 -3=0
{(x-1)-1}^2=4
(x-2)^2=4
x=0 x=4
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