(2√5-√15)(√15+2√5)помогите

Question

(2√5-√15)(√15+2√5)
помогите

Answer 1

(2√5-√15)(√15+2√5)=
2√5×√15+2√5×2√5-√15×√15-√15×2√5=
2√75+4×5-15-2√75=20-17= 3