Tolong dong nomer 19 sama 20 pakai cara yah

4√18 - √50 = 4 √2.9 - √2.25
= 4.3 √2 - 5√2
= 12√2 - 5√2
= 7√2

√25-16 / √25-16
= √9 / √9
= 3/3
=1