merasionalkan... √2 per 4-√20???

√2 / 4-√20 X 4+√20 / 4+√20
4√2 + √40 / 16-4√20+4√20-20
4√2 + 2√10 / -4
2(2√2 + 2√10) /-4
2√2+2√10/-2

√2÷4-√20 x 4+√20 ÷4+√20
 = 4√2 + √40 ÷ 16 - 4√20 + 4√20 - 20
 = 4√2 + 2√10 ÷ -4
= 2 (2√2 +√10) ÷ -4