Answer:
Step-by-step explanation:
Rational number
[tex]1) \dfrac{4}{5}+\dfrac{3}{8}\\\\\dfrac{4}{5} \ \text{is a rational number} \ and \ \dfrac{3}{8} \ \text{is a rational number}\\\\\dfrac{4}{5}+\dfrac{3}{8} \ \text{is also a rational number}[/tex]
[tex]b) \sqrt{100}+\sqrt{5} = 10+\sqrt{5}\\\\\sqrt{5} \ \text{is a irrational number}. \\\\ \text{Rational number added to irrational number will result in an irrational number}\\\\10 + \sqrt{5} \ is \ not \ a \ rational \ number.[/tex]
c)
[tex]7\sqrt{5}-\sqrt{245}=7\sqrt{5}-\sqrt{7*7*5}[/tex]
[tex]= 7\sqrt{5}-7\sqrt{5}\\\\=0\\\\\text{\bf $ 7\sqrt{5}-\sqrt{245}$ ia a rational number}[/tex]
d)
[tex](4\sqrt{7})*(2\sqrt{7})=4*2*\sqrt{7*7}\\[/tex]
= 4*2*7
= 56
[tex]4\sqrt{7}*2\sqrt{7} \ \text{\bf is a rational number}[/tex]
