This is a test question of binary linear equations A new operation "*" is defined for real numbers x and Y. x * y = ax + by (A and B are constants). On the right side of the equation are the usual addition and multiplication operations. It is known that 3 * 5 = 15 and 4 * 7 = 28. What is a + B?
3*5=15=3a+5b,
4*7=28=4a+7b
By solving the equations, a = - 35, B = 24
That is to say, x = 3Y = 5 and x = 4Y = 7 are brought into the new operation
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