√5+ (1/√5 + 1/√2) · √10 - ( 1/√8 - 1/√20) · 4√10 - 5√2 =
= √5+ ( √5/5 + √2/2)×√10 - (1/2√2 - 1/ 2√5 ) × 4√10 - 5√2
= √5 + √50/5 + √20/2 - (√2/4 - √5/10) × 4√10 - 5√2
= √5 + 5√2/5 + 2√5/2 - ( √20 - 2√50/5) - 5√2
= √5 + √2 + √5 - ( 2√5 - 10√2/5) - 5√2
= √5 + √2 + √5 - ( 2√5 - 2√2) - 5√2
= √5 + √2 + √5 - 2√5 + 2√2 - 5√2
= 0 - 2√2
= -2√2
