<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
<span>Восстановите стертые числа.</span>
10 23 16
25 15 9
14 11 24