а) x/(ax+ay) + y/(by+bx) = 1/a + 1/b
б) a/(cb) - c/(db) = (a-d) / (cb)
в) b/(7b+7c) + c/(7b-7c) = 1/7
г) 3a/(10a-20) - 3a/(10a+20) = 3a/10(a-2) - 3a/10(a+2) = 3a/10[(a-2)-(a+2)] = -3/10
а) x/(ax+ay) + y/(by+bx) = 1/a + 1/b
б) a/(cb) - c/(db) = (a-d) / (cb)
в) b/(7b+7c) + c/(7b-7c) = 1/7
г) 3a/(10a-20) - 3a/(10a+20) = 3a/10(a-2) - 3a/10(a+2) = 3a/10[(a-2)-(a+2)] = -3/10