в)
4x 2 − 1 4x 2 − 1 =x(10x-9); =10x2-9x; 3 3
4x 2 − 1 =0; 30x2-27x-4x2+1=0; 3 26x2-27x+1=0; D=272-4 ⋅ 26 ⋅ 1=729-104=625=252; 27 ± 25 x= ; 52 27 + 25 =1; x1= 52 27 − 25 1 ; x2= = 52 26 3 2 4 3 3 2 4 3 г) x2- x= x2+ ; x2- x- x2- =0; 4 5 5 4 4 5 5 4
10x2-9x-
15x2-8x-16x2-15=0; x2+8x+15=0; D1=42-1 ⋅ 15=1; x=
−4 ± 1 ; 1
x1=-4+1=-3; x2=-4=1=-5. №548. a) 5x2-x-1=0; D=12-4 ⋅ 5 ⋅ (-1)=21; 1 ± 21 1 ± 21 1 ± 4б58 = ≈ ; 2⋅5 10 10 1 + 4,58 5,58 x1 ≈ = = 0,558 ≈ 0,56 ; 10 10 1 − 4,58 3,58 =− = −0,358 ≈ −0,36 ; x2 ≈ 10 10 2 б) 2x +7x+4=0; D=72-4 ⋅ 2 ⋅ 4=17;
x=
− 7 ± 17 − 7 ± 17 − 7 ± 4,12 = ≈ ; 2⋅2 4 4 11,12 −7 − 4,12 x1 ≈ =− = −2,78 ; 4 4 −7 + 4,12 −2,88 x2 ≈ = = −0,72 ; 4 4
x=
в) 3(y2-2)-y=0; 3y2-y-6=0; D=12-4 ⋅ 3 ⋅ (-6)=1+72=73;
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