곱셈공식

곱셈공식	㉠ (a+b)²=a²+2ab+b², (a-b)²=a²-2ab+b² ㉡ (a+b)(a-b)=a²-b² ㉢ (x+a)(x+b)=x²+(a+b)x+ab ㉣ (ax+b)(cx+d)=acx²+(bc+ad)x+bd

곱셈공식
(multiplying formular)

㉠ (x+3)²=x²+2·x·3+3·2=x²+6x+9
(x-3)²=x²-2·x·3+3·2=x²-6x+9
㉡ (x+3)(x-3)=x²-3²=x²-9
㉢ (x+2)(x+3)=x²+(2+3)x+2·3=x²+5x+6
㉣ (2x+3)(3x+2)=2·3x²+(9+4)x+3·2=6x²+13x+6

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