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$(x+4)(x+9)$

Write the coefficient of $x^{2}$ in each of the following:

$(i)$ $\frac{\pi}{6} x+x^{2}-1$

$(ii)$ $3 x-5$

Which of the following expressions are polynomials in one variable and which are not $?$ State reason for your answer. If the given expression is a polynomial, state whether it is a polynomial in one variable or not

$\pi x^{2}-\sqrt{3} x+11$

Verify whether $2$ and $5$ are zeros of the polynomial $x^{2}-2 x-15$ or not.

Find the value of the polynomial $x^{2}-7 x+12$ at.

$x=\frac{1}{2}$