2
9 − 113 − 9 9 − 113 − 2 = 4 8 8
=4 =
81 − 18 113 + 113 81 − 9 113 − −2 = 64 8
97 − 9 113 81 − 9 113 97 9 113 81 9 113 − −2 = − − + −2 = 2−2 = 0. 8 8 8 8 8 8
№644. a) x2-2x-2=0; D1=(-1)2-1 ⋅ (-2)=1+2=3; x=1 ± 3 ≈ 1 ± 1,73 ; x1 ≈ 1+1,73=2,73; x2 ≈ 1-1,73=-0,73; б) x2+5x+3=0; D=52-4 ⋅ 1 ⋅ 3=25-12=13; − 5 ± 13 − 5 ± 3,61 ; ≈ 2 2 −5 + 3,61 1,39 =− = −0,695 ≈ −0,70 ; x1 ≈ 2 2 −5 = 3,61 −8,61 = = −4,305 ≈ −4,30 ; x2 ≈ 2 2
x=
в) 3x2-7x+3=0; D=(-7)2-4 ⋅ 3v3=13; 7 ± 13 7 ± 3,61 ≈ ; 3⋅ 2 6 7 − 3,61 3,39 = ≈ 0,57 ; x1 ≈ 6 6 7 + 3,61 10,61 = ≈ 1,77 ; x2 ≈ 6 6
x1,2=
г) 5x2+31x+20=0; D=312-4 ⋅ 5 ⋅ 20=961-400=561; − 31 ± 561 − 31 ± 23,69 ≈ ; 5⋅ 2 10 7,31 −31 + 23,69 x1 ≈ =− ≈ −0,73 ; 10 10
x=
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