2) - 4x^3( x^2 - 3x + 2) = - 4x^5 + 12x^4 - 8x^3
3) ( 1 - x)(2y + x) = 2y + x - 2xy - x^2 = - x^2 - 2xy + x + 2y
4) (5c - 4)^2 = 25c^2 - 40c + 16
<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
30% от 40 = 0,3*40=12уч. - спорт.секции
25% от 12 = 0,25*12=3 уч. = басктебол
B^2+10b+25\b-25=(b+5)(b+5)\(b-5)(b+5)=b+5\b-5