곱셈공식과 곱셈공식의 변형1. 곱셈공식1. $\left(a+b+c\right)^{2}$ $=a^{2}+b^{2}+c^{2}+2ab+2bc+2ca$ 2. $\left(a+b\right)^{3}=a^{3}+3a^{2}b+3ab^{2}+b^{3}$ $\left(a-b\right)^{3}=a^{3}-3a^{2}b+3ab^{2}-b^{3}$ 3. $\left(a+b\right)\left(a^{2}-ab+b^{2}\right)=a^{3}+b^{3}$ $\left(a-b\right)\left(a^{2}+ab+b^{2}\right)=a^{3}-b^{3}$ 4. $\left(a^{2}+ab+b^{2}\right)\left(a^{2}-ab+b^{2}\right)$ $=a^{4}+a^{2}b^{2}+b^{4}$ 5. $\l..