Question

Calculați:
2(3-√5)-4(-1+2√5)+10(√5-2)

(5 supra√63-2 supra √7+3 supra√28):(-radical mare7supra9)

Answer 1

a)2(3-√5)-4(-1+2√5)+10(√5-2)=6-2√5+4-8√5+10√5-20=-10
b)$\frac{5}{ \sqrt{63} } - \frac{2}{ \sqrt{7} } + \frac{3}{ \sqrt{28} }= \frac{5}{3 \sqrt{7} } - \frac{2}{ \sqrt{7} }+ \frac{3}{2 \sqrt{7} } = \frac{10-12+6}{6 \sqrt{7} }= \frac{4}{6 \sqrt{7} } = \\ = \frac{2}{3 \sqrt{7} }= \frac{2 \sqrt{7} }{63}$