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Find the following as a single complex number x + iy:

(i) (5 + 9 i) (-3 + 4 i)

(ii) (-2 - 5 i) (3 - 6 i)

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(i)  (5 + 9 i) (-3 + 4 i)

= 5(-3 + 4 i ) +9 i(-3 + 4 i)

= -15 + 20 i -27 i +36 i2

= -15 - 7 i - 36

= -51 - 7 i

x = -51 y = -7

(II) (-2 - 5 i) (3 - 6 i)

 = -2(3 - 6 i) -5 i(3 - 6 i)

= -6 + 12 i - 15 i + 30 i2

= -6 -3 i +30

= 24 - 3 i

= x = 24 y = -3

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