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Express each of the following in the form (a + ib) : `{:((i),(3+sqrt(-5))(3-sqrt(-5)),(ii),(-2+sqrt(-3))(-3 + 2 sqrt(-3))),((iii),(-2+3i)^(2),(iv),(sqrt(5)-7i)^(2)):}` |
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Answer» We have `(i)" "(3+sqrt(-5))(3-sqrt(-5))=(3+sqrt(5)i)(3-sqrt(5)i)={3^(2)-(sqrt(5)i)^(2)}` `=(9-5i^(2))=(9+5)=14 + 0i." "[because (z_(1) + z_(2))(z_(1)-z_(2))=(z_(1)^(2)-z_(2)^(2))]` `(ii)" "(-2+sqrt(-3))(-3+2 sqrt(-3))=(-2+sqrt(3)i)(-3+2sqrt(3)i)` `=(6-4 sqrt(3)i - 3 sqrt(3)i + 6i^(2))` `=-7 sqrt(3)i = 0 - 7 sqrt(3)i`. `(iii)" "(-2+3i)^(2)=(-2)^(2)+(3i)^(2)+2 xx (-2) xx 3i` `=(4+9i^(2)-12i)=(4-9-12i)=(-5-12i)`. `(iv)" "(sqrt(5)-7i)^(2)=(5)^(2)+(7i)^(2)-2 xx sqrt(5) xx 7i` `=(25+49i^(2)-14 sqrt(5)i)=(25-49-14 sqrt(5)i)` `=(-24-14 sqrt(5)i)`. |
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