Given expression:
2x(x + 7)-(3x +1);
To distribute implies to spread a process equally in an expression. Often times, the distributive property is used for expressions inside parentheses;
2x(x + 7)-(3x +1)
Distribute 2x over the first parentheses;
the negative sign distributes over the second part
= (2x² + 14x) - 3x -1
= 2x² + 14x -3x -1
Add like terms;
= 2x² + 11x -1
This expression 2x² + 11x -1 is equal to the given one
It looks like you might have intended to say the roots are 7 + i and 5 - i, judging by the extra space between 7 and i.
The simplest polynomial with these characteristics would be

but seeing as each of the options appears to be a quartic polynomial, I suspect f(x) is also supposed to have only real coefficients. In that case, we need to pair up any complex root with its conjugate to "complete" f(x). We end up with

which appears to most closely resemble the third option. Upon expanding, we see f(x) does indeed have real coefficients:

The correct answer is 5460 cubic feet or 5460 
Explanation:
The silo has a cylindrical shape, in this context, the volume of the silo or any other cylinder can be calculated by using the formula
. In this formula the symbol
refers to the number 3.1415..., the letter
refers to the radius of the base and the letter
refers to the height.
Moreover, in this case, it is known the heigh (21 feet) and the area of the base (260 square feet). Additionally, this area of the base is the result of the formula
, which is exactly the first section of the formula to find the volume. This implies that by multiplying the area of the base by the height the volume is known. Here is the process:
or
(Area of the base × height)
× 

scientist A dissolved 1 kg of salt in 3 litres.
scientist B dissolved 20 pounds of slat in 7 pint of water.
we know that 1 pound =0.543 g
20 pounds=9.07 kg.
1 pint=0.5 litres
so 7 pints =3.5 litres
so dissoving 1 kg of salt in 3 litres of water and 9.07 kg in 3.5 litres of water
we know that for concentration kg/l units is used .
for A= 1/3=0.33kg/l
and B=9.07/3.5=2.59 kg/l.
so scientist A has prepared more concentrated solution .
<h2>2 units down</h2><h2>1 unit to the left</h2>