Question
Express the following complex numbers in the standard form a + ib: $(1+\text{i})(1+2\text{i})$

Answer

$(1+\text{i})(1+2\text{i})=1\times(1+2\text{i})+\text{i}(1+2\text{i})$ $=1+2\text{i}+\text{i}+2\text{i}^2$ $=1+3\text{i}-2$ $=-1+3\text{i}$ $\therefore \ (1+\text{i})(1+2\text{i})=-1+3\text{i}$

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