## Precalculus: Mathematics for Calculus, 7th Edition

$(2+5i)^{2} = -21+20i$
1. $(2+5i)^{2}$ 2. Multiply $(2+5i)\times(2+5i)$(use the FOIL method to distribute the First, Outer, Inner, and Last terms):$4+10i+10i+25i^{2}$ 3. Combine like terms: $4+20i+25i^{2}$ 4. Change $25i^{2}$ to -25 because $i^{2} = -1$ and $25\times-1 = -25$:$4+20i-25$ 5. Combine like terms:$-21+20i$