To divide complex numbers, we multiply the numerator and denominator by the conjugate of the denominator.
a. 3−2i4i=(3−2i)(3+2i)4i(3+2i)=9−(4i2)12i+8i2=9+412i−8=13−8+12i=−138+1312i b. 3+7i2+5i=(3+7i)(3−7i)(2+5i)(3−7i)=9−49i26−14i+15i−35i2=9+496+i+35=5841+i=5841+581i c. −3+7i4−10i=(−3+7i)(−3−7i)(4−10i)(−3−7i)=9−49i2−12−28i+30i+70i2=9+49−12+2i−70=58−82+2i=29−41+i=−2941+291i d. −2−3i−1−i=(−2−3i)(−2+3i)(−1−i)(−2+3i)=4−9i22−3i+2i−3i2=4+92−i+3=135−i=135−131i e. 4−i3+9i=(4−i)(4+i)(3+9i)(4+i)=16−i212+3i+36i+9i2=16+112+39i−9=173+39i=173+1739i f. −3−6i−4+9i=(−3−6i)(−3+6i)(−4+9i)(−3+6i)=9−36i212−24i−27i+54i2=9+3612−51i−54=45−42−51i=15−14−17i=−1514−1517i