These are the steps needed for this question hope this helps if there is any more questions do feel free to ask them
Hello :
<span>7x-2y=1 ...(1)
2y=x-1...(2)
</span><span>substitution 2y in (1) :
</span>7x-(x-1) = 1
7x-x+1 = 1
7x = 0
x=0
in (2) : 2y = 0-1
2y = -1 y= -1/2
the <span>system have one solution : (0 ;-1/2)</span>
the radius: r^2 = 81
r =9
c = 2*pi*r
= 2 * pi * 9
= 18 *pi
Answer: 18*pi or approximately 56.62
Answer:7
Step-by-step explanation:
We know that
the equation of a sphere is
(x-h)²+(y-k)²+(z-l)²=r²
where (h,k,l) is the center and r is the radius
we have
x²+y²+z²<span>−2x−4y+8z+17=0
</span>
Group terms that contain the same variable, and move the
constant to the opposite side of the equation
(x²+2x)+(y²-4y)+(z²+8z)=-17
<span>Complete
the square. Remember to balance the equation by adding the same constants
to each side
</span>(x²+2x+1)+(y²-4y+4)+(z²+8z+16)=-17+1+4+16
(x²+2x+1)+(y²-4y+4)+(z²+8z+16)=4
Rewrite as perfect squares
(x+1)²+(y-2²)+(z+4)²=4
(x+1)²+(y-2²)+(z+4)²=2²
the center is the point (-1,2,-4) and the radius is 2 units
