This question is based on concept of squares and monomial. Therefore, the correct option is (1) i.e. 121:11.
In this question, we have to determined that which expression represents a perfect square monomial and it’s square root.
Now check all the options,
(1) 121;11
We know that square of 11 is,
[tex]\bold{11^{2} = 121 }[/tex]
(2) [tex]\bold{4x^{2} ;2x }[/tex]
We know that square of 2x is,
[tex]\bold{2x = 4x^{2} }[/tex]
(3) [tex]\bold{9x^{2} -1;3x-1 }[/tex]
Now solve it,
[tex]\bold{ ({3x - 1} )^ {2} =9x^{2}+1-6x\neq 9x^{2} -1 }[/tex]
(4) 25x; 5x
We know that square of 5x is,
[tex]\bold{5x = 25x^{2} \neq 25x }[/tex]
(5)[tex]\bold {49x^{4} ;7x^{2} }[/tex]
We know that square of [tex]7x^{2}[/tex] is,
[tex]\bold{7x ^2= 49x^{4} }[/tex]
Therefore, the correct option is (1) i.e. 121:11.
For more details, please refer this link:
https://brainly.com/question/13647939
