Question

Розв'яжіть систему рівнянь x-2y=5 x²-2xy-3y²=-7

Answer 1

Ответ:

(x-2y)(y-3x)+(x+y)(x-3y)-(y-3x)(4x-5y);

=(xy-3x²-2y²+6xy)+(x²-3xy+xy-3y²)-(4xy-5y²-12x²+15xy);

=7xy-3x²-2y²+(x²-2xy-3y²)-(19xy-5y²-12x²);

=7xy-3x²-2y²+x²-2xy-3y²-19xy+5y²+12x²;

=(-3+1+12)x²+(7-2-19)xy+(-2-3+5)y²;

=10x²-14xy;

=2x(5x-7y)

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Объяснение: