<span>1) 6x^2+7xy-20y^2=6x</span>²-8xy+15xy-20y²=2x(3x-4y)+5y(3x-4y)=<span>(3x-4y)(2x+5y)
2) 4x</span>²-2x-1=4*(x-(1+√5)/4)(x-(1-√5)/4)<span>
D=4+16=20=4*5
x</span>₁=(2+2*√5)/8=(1+√5)/4
x₂=(1-√5)/4
Sin²a=1:(1+ctg²a)=1:(1+8)=1/9
sina=1/3
cos²a=1-1/9=8/9
cosa=2√2/3
27sin2a/√2=54sinacosa/√2==54*1/3*2√2/3:√2=12
7(-3+2х)=-6х-1
-21+14х=-6х-1
14х+6х=-1+21
20х=20
х=1
(3x² -7x+2)/(2-6x) =3(x-1/3)(x-2)/(-6(x-1/3)) = (2-x)/2 . * * * x≠1/3 * * *
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(x+40)/(x³-16x) :((x-4)/(3x² +11x-4) - 16/(16-x²)) =
(x+40)/x(x²-16) :( (x-4)/3(x+4)(x-1/3) +16/(x² -16))=
(x+40)/x(x²-16) :( (x-4)/(x+4)(3x-1) +16/(x² -16))=
(x+40)/x(x²-16) :( ((x-4)² +16(3x-1)) /(x²-16)(3x-1))=
(x+40)/x(x²-16) :( (x²-8x+16 +48x-16) / (x²-16)(3x-1)) =
x+40)/x(x²-16) :( (x² +40x) / (x²-16)(3x-1))
(x+40)/x(x²-16) *(x²-16)(3x-1)/(x²+40) = (3x-1)/x * * * x≠<span>±4 * * *</span>