Respuesta :
Answer:
The correct option is 3.
Step-by-step explanation:
The given expression is
[tex]7\sqrt{28}-5\sqrt{63}[/tex]
It can be written as
[tex]7\sqrt{4\times 7}-5\sqrt{9\times 7}[/tex]
[tex]7\sqrt{2^2\times 7}-5\sqrt{3^2\times 7}[/tex]
Using product property of radical expressions, we get
[tex]7(\sqrt{2^2}\times \sqrt{7})-5(\sqrt{3^2}\times \sqrt{7})[/tex] [tex][\because \sqrt{ab}=\sqrt{a}\sqrt{b}][/tex]
[tex]7(2\times \sqrt{7})-5(3\times \sqrt{7})[/tex]
[tex]14\sqrt{7}-15\sqrt{7}[/tex]
Taking out common factors.
[tex]\sqrt{7}(14-15)[/tex]
[tex]\sqrt{7}(-1)[/tex]
[tex]-\sqrt{7}[/tex]
Therefore the correct option is 3.
