ANSWER

EXPLANATION
The equation of the circle with radius r and centre (a,b) is given by

The radius is

We need to determine the center of the circle from the given equation of another circle, which is,

We complete the square to obtain,





The centre of this circle is (4,3)
Hence the center of the circle whose equation we want to find is also (4,3).
With this center and radius 2, the required equation is,

Therefore the correct answer is C.
1. (3 + xz)(–3 + xz)
2. (y² – xy)(y² + xy)
3. (64y2 + x2)(–x2 + 64y2)
Explanation
The difference of 2 squares is in the form (a+b)(a-c).
(3 + xz)(–3 + xz) = (3 + xz)(xz -3)
= (xz + 3)(xz - 3)
= x²y²-3xy+3xy-9
=x²y² - 3²
(y² – xy)(y² + xy) = y⁴+xy³-xy³-x²y²
= y⁴ - x²y²
(64y2 + x2)(–x2 + 64y2)= (64y²+x²)(64y²-x²)
= 4096y⁴-64y²x²+64y²x²-x⁴
= 4096y⁴ - x⁴
4(x+7) becomes 4x+28 you multipli the 4 in parentheses ans 2(x+7) becomes 2x+14
4x+28=2x+14 you move the x termes to the left and other numbers to the right look:
4x-2x=14-28 when you change the sides always change the sign +or-
2x=-14
2x/2=-14/2
X=-7