Which expressions represent a perfect square monomial and its square root? Check all that apply.121; 114x2; 2x9x2 – 1; 3x - 125x; 5x49x4; 7x2

A perfect square monomial has coefficients and variable exponents that are squares, and its square root has half the variable exponents. The square roots of 121, 4x², and 49x⁴ are 11, 2x, and 7x², respectively, so A, B, and E are correct. Choice C includes subtraction, so it is not a monomial, and 25x has square root 5√x, not 5x.

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