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2009-12-14T19:17:10+01:00
1. ...10x+15-6x²-9x+6x²-42x-x+7=0
-42x=-22 /:(-42)
x=22/42
x=11/21
2. a+b=3
1/a + 1/b = 2

a=3-b
1/(3-b) + 1/b = 2 / *b

a=3-b
½ + 1 = 2b

a=3-b
1,5 = 2b /:2

a=3-b
¾ = b

a=3-¾
a=2¼ :)
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2009-12-14T19:29:14+01:00
1.5-3x=0 2x+3=0 6x-1=0 x-7=0
3x=5 2x=-3 6x=1 x=7
x=5/3 x=-3/2 x=1/6

2.x+y=3 x=3-y
1/x+1/y=2,4/*x*y
y+x=2,4*x*y
y+3-y=2,4*(3-y)*y
3=7,2y-2,4y²
-2,4y²+7,2y-3=0
Δ=b²-4ac
51,84-28,8=23,04
√Δ=4,8
x₁=-b-√Δ/2a
(-7,2-4,8)/2*(-2,4)=-12/(-4,8)=2,5
x2=-2,4/(-4,8)=½


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