12/06/22 01:10:35.44
>>647
そだね。これでどうかな。
x, y > 0 のとき
(-x) * (-y) = x * 0 + (-x) * (-y) = x * (y - y) + (-x) * (-y) = x * y + x * (-y) + (-x) * (-y) = x * y + (x - x) * (-y) = x * y
12/06/22 01:10:35.44
>>647
そだね。これでどうかな。
x, y > 0 のとき
(-x) * (-y) = x * 0 + (-x) * (-y) = x * (y - y) + (-x) * (-y) = x * y + x * (-y) + (-x) * (-y) = x * y + (x - x) * (-y) = x * y