(-a*x+2*y)*(3*x+b*y)=c*x^2+7*x*y+y^2 найти c

(-a*x+2*y)*(3*x+b*y)=c*x²+7*x*y+y²
-3ax²+6xy-abcxy+2by² = cx²+7xy+y²
3ax²+6xy-abcxy+2by² - (cx²+7xy+y²) = 0
3ax²+6xy-abcxy+2by² - cx²-7xy-y² = 0
2by²-y²-abxy-xy-cx²-3ax²=0

cx² = 2by²-y²-abxy-xy-3ax²
c = (2by²-y²-abxy-xy-3ax²)/x²