Answer to Question 1
Market failures are undesirable social results associated with free market outcomes. They include the growth of monopoly power, the presence of externalities, a lack of public goods and services, and an inequitable distribution of income. Government can intervene by enforcing anti-trust, tax or subsidize externalities, provide for public goods and redistribute income to correct for market failures.
Answer to Question 2
An increase in demand will increase equilibrium price and quantity; and vice versa. An increase in supply will decrease equilibrium price and increase the equilibrium quantity; and vice versa. A simultaneous increase in demand and supply will assuredly increase the equilibrium quantity but the impact on equilibrium price is uncertain. A simultaneous increase in demand and decrease in supply will assuredly increase the equilibrium price but the impact on equilibrium quantity is uncertain.