Question

-2radical din 80+radical din320-4radical din20+radical din45

Answer 1

$-2 \sqrt{80} + \sqrt{320} -4 \sqrt{20} + \sqrt{45} = \\ =-2 \cdot 4 \sqrt{5} +8 \sqrt{5} -4 \cdot 2 \sqrt{5} +3 \sqrt{5} = \\ =-8 \sqrt{5} +8 \sqrt{5} -8 \sqrt{5} +3 \sqrt{5} = \\ =-5 \sqrt{5}$