Let $\alpha$ and $\beta$ be the roots of the quadratic equation $ax^2 + bx + c = 0$. If $a, b, c$ are in $A.P.$ and $\alpha + \beta = 15$,then $\alpha\beta$ equals:

Find the value of $a^{2}+b^{2}+c^{2}-2ab+2ac-2bc$,if $a=x+y$,$b=x-y$,and $c=2x-1$.

The diagram shows the graph of $y = ax^2 + bx + c$. Then:

Solve the given two equations and select the correct answer from the given options.
$I.$ $13x - 21 = 200 - 4x$
$II.$ $y = \sqrt[3]{2197}$

Solve the given two equations and select the correct answer from the given options.
$I.$ $\sqrt{784} x + 1234 = 1486$
$II.$ $\sqrt{1089} y + 2081 = 2345$

$Quantity \, 1:$ Original duration of flight. In a flight of $3000 \, km$,an aircraft was slowed down by bad weather. Its average speed for the trip was reduced by $100 \, km/hr$ and the time increased by $1 \, hour$.
$Quantity \, 2:$ Usual time of a man who,when walking at $\frac{3}{4}$ of his usual pace,reaches his office $20 \, minutes$ late.