(2x + 10)(x - 9)
2x(x - 9) + 10(x - 9)
2x(x) - 2x(9) + 10(x) - 10(9)
2x² - 18x + 10x - 90
2x² - 8x - 90
We can say that:
8x = -2ax
8 = -2a
a = -4
22y = - 2by
22 = -2b
b = -11
37 = a² + b² - r²
37 = (-4)² + (-11)² - r²
r² = 16 + 121 - 37
r² = 100
r = 10
With all this information, we can say that:
The center of the circle is: (-4 ; -11)
and the radius of the circle is r = 10
P.S:
(a - x)² + (b-y)² = r²
a² - 2ax + x² + b² -2by + y² - r² = 0
x² + y² -2ax - 2by + a² + b² - r² = 0
Essentially when people ask you find the solution to system of equation, there asking at what x value do these to graphs intersect. The easiest way to do this is to get a graphing calculator, or desmos and type in the equation and find where they intersect. Heck, even the question says to solve it with a graph, but I'll demonstrate it algebraically.
One way you can do this is set the equation equal to each other. This is because you want to know at what x-value has the same y-value. So we get:
x^2 + 6x + 8 = x + 4
We can then combine like terms, or move everything to one side. So we get:
x^2 + 5x + 4 = 0.
Then we can use the quadratic formula to solve for x.
x=(-5 +/- sqrt(5^2 - 4(1)(4)))/(2(1)
This simplifies into:
(-5 +/- 3)/2
Finally we add and subtract:
(-5 + 3)/2 = x = -1
(-5 - 3)/2 = x = -4
And our solution is x = -1, x = -4
It is very simple it would be positive but would remain 35
The appropriate formula is C = 2*pi*r.
Here, C = 2*pi*(50 units) = 100*pi units (answer)