Question

Solve the system using combination method to get a solution (x,y) 4x+7y=10 -4x-6y=28

Answer 1

$4x+7y=10\\ -4x-6y=28\\ -------\\ y=38\\\\ 4x+7\cdot38=10\\ 4x+266=10\\ 4x=-256\\ x=-64$

Answer 2

$\left \{ {{4x+7y=10} \atop {-4x-6y=28}} \right. \\\\add\ those\ two\ equations\\\\ y=38\\\\ 4x+7y=10\ \ \ | subtract\ 7y\\\\ 4x=10-7x\ \ \ \ | divide\ by\ 4\\\\ x=\frac{10-7x}{4}=\frac{10-7*38}{4}=\frac{10-266}{4}=\frac{-256}{4}=-64\\\\ solution:\\ \left \{ {{y=38} \atop {x=-64}} \right.$