Which expressions are polynomials?

Select each correct answer.

4x

6y2 + 5x

7y2+9x

4x

Step-by-step explanation:

The polynomial expression is in the form:

f (x) = aₙxⁿ + aₙ₋₁xⁿ⁻¹ + aₙ₋₂xⁿ⁻² + ... + a₀

Polynomial have one variable so,

6y² + 5x

7y² + 9x

are not polynomial

Also since 4x is satisfying the expression of polynomial, Thus it is only polynomial in the given set of options.

Im pretty sure it's 7y2+9x / : 6y2+5x