298*302+4 205^2 简便运算
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298*302+4 205^2 简便运算
![298*302+4 205^2 简便运算](/uploads/image/z/19058823-63-3.jpg?t=298%2A302%2B4+205%5E2+%E7%AE%80%E4%BE%BF%E8%BF%90%E7%AE%97)
298 X 302 + 4
= ( 300 - 2 )( 300 + 2 ) + 4
= 300" - 2" + 4
= 90000 - 4 + 4
= 90000
205"
= 205" - 5" + 5"
= ( 205 - 5 )( 205 + 5 ) + 25
= 200 X 210 + 25
= 42000 + 25
= 42025
= ( 300 - 2 )( 300 + 2 ) + 4
= 300" - 2" + 4
= 90000 - 4 + 4
= 90000
205"
= 205" - 5" + 5"
= ( 205 - 5 )( 205 + 5 ) + 25
= 200 X 210 + 25
= 42000 + 25
= 42025