Question

СРОЧНО! ПОМОГИТЕ! БУДУ ОЧЕНЬ БЛАГОДАРНА! Розв’яжіть систему способом додавання (решить систему способом сложения), нужно только 81 и 82

Answer 1

$81) \ \left \{ {{\dfrac{x + 1}{3} - \dfrac{y + 2}{4} = \dfrac{2(x - y)}{5} \ \bigg {\ \ \ | \cdotp 60}} \atop {\dfrac{x - 3}{4} - \dfrac{y - 3}{3} = \ \bigg {2y - x} \ \ \ \ \ \bigg{\ | \cdotp 12} }} \right.$

$\left \{ {{\bigg{20(x + 1) - 15(y + 2) = 24(x - y)}} \atop {\bigg{3(x-3) - 4(y-3) = 12(2y - x)}}} \right.$

$\left \{ {{\bigg{20x + 20 - 15y - 30 = 24x - 24y}} \atop {\bigg{3x -9 - 4y + 12 = 24y - 12x \ \ }}} \right.$

$\left \{ {{\bigg{-4x + 9y = 10 \ \ \ \ \ \ | \ \cdotp 15 }} \atop {\bigg{15x - 28y = -3 \ \ \ \ | \ \cdotp 4}}} \right.$

$\left \{ {{\bigg{-60x + 135y = 150} \atop {\bigg {60x - 112y = -12}} \right.$

$\left \{ {{\bigg{23y = 138 \Rightarrow y = 6 \ \ \ \ \ \ \ \ }} \atop {\bigg{-4x + 9 \ \cdotp 6 = 10 \Rightarrow x = 11}}} \right.$

Ответ: x = 11; y = 6

$82) \ \left \{ {{\bigg{\ (x + 3)(y + 5) = (x + 1)(y + 8) \ \ \ \ \ \ }} \atop {\bigg{\ (2x - 3)(5y + 7) = 2(5x - 6)(y + 1)}}} \right.$

$\left \{ {{\bigg{xy + 5x + 3y + 15 = xy + 8x + y + 8 \ \ \ \ \ \ \ \ \ \ \ \ \ \ }} \atop {\bigg{10xy + 14x - 15y - 21 = 10xy + 10x - 12y - 12}}} \right.$

$\left \{ {{\bigg {-3x + 2y = -7 \ \ \ \ \ | \ \cdotp 3}} \atop {\bigg{4x - 3y = 9 \ \ \ \ \ \ \ \ | \ \cdotp 2}}} \right.$

$\left \{ {{\bigg{-9x +6y = -21}} \atop {\bigg{8x - 6y = 18 \ \ \ }}} \right.$

$\left \{ {{\bigg{-x= -3 \Rightarrow x = 3 \ \ \ \ \ \ \ \ \ \ }} \atop {\bigg {-3 \ \cdotp 3 + 2y = -7 \Rightarrow y = 1}}} \right.$

Ответ: x = 3; y = 1