13. Mostly pure carbon (coal) will burn in sufficient oxygen to produce carbon dioxide. In an experiment 8.40 g of reacts with oxygen and 30.80 g of carbon dioxide is produced. a. Write a balanced chemical equation. b. What mass of oxygen reacted with the 8.40 grams of C ? c. Calculate the percentage composition of the carbon dioxide.

Use the Leading Coefficient Test to determine the end behavior of the graph of the given polynomial function. \( f(x)=8 x^{4}+3 x^{3}-7 x+5 \) Choose the correct answer below. A. The graph of \( f(x) \) falls to the left and rises to the right B. The graph of \( f(x) \) rises to the left and falls to the right. C. The graph of \( f(x) \) falls to the left and falls to the right. D. The graph of \( f(x) \) rises to the left and rises to the right

Determine if the function is a polynomial function. If it is, state its degree and leading coefficient a. \( f(x)=6 x^{5}-\sqrt[5]{x} \)

Second : If \( \triangle A B C \) is an obtuse-angled triangle \( \therefore m(\angle B D C)=180^{\circ}-m(\angle A) \) \( \therefore \sin \left(180^{\circ}-A\right)=\frac{B C}{B D} \) \( \therefore \sin A=\frac{a}{2 r} \) \( \therefore \frac{a}{\sin A}=\frac{b}{\sin B}=\frac{c}{\sin C}=2 r \)

\( 1< \) Select the correct choice that completes the sentence below.

Multiply. \[ (w-2)(w+7) \]