Answer:
9
Step-by-step explanation:
Compare your x2 + y2=81 to the following:
x^2 + y^2 = 81
The " ^ " symbol indicates exponentiation.
Now compare x^2 + y^2 = 81 to
x^2 + y^2 = r^2.
This is the standard equation of a circle of radius r centered at the origin, (0,0). You can see for yourself that 81 must equal r^2.
Taking the square root of 81, we get plus or minus 9.
But the radius must be positive, so we reject the -9 and take +9.
The radius is 9.
Answer:
A. (0, -2) and (4, 1)
B. Slope (m) = ¾
C. y - 1 = ¾(x - 4)
D. y = ¾x - 2
E. -¾x + y = -2
Step-by-step explanation:
A. Two points on the line from the graph are: (0, -2) and (4, 1)
B. The slope can be calculated using two points, (0, -2) and (4, 1):

Slope (m) = ¾
C. Equation in point-slope form is represented as y - b = m(x - a). Where,
(a, b) = any point on the graph.
m = slope.
Substitute (a, b) = (4, 1), and m = ¾ into the point-slope equation, y - b = m(x - a).
Thus:
y - 1 = ¾(x - 4)
D. Equation in slope-intercept form, can be written as y = mx + b.
Thus, using the equation in (C), rewrite to get the equation in slope-intercept form.
y - 1 = ¾(x - 4)
4(y - 1) = 3(x - 4)
4y - 4 = 3x - 12
4y = 3x - 12 + 4
4y = 3x - 8
y = ¾x - 8/4
y = ¾x - 2
E. Convert the equation in (D) to standard form:
y = ¾x - 2
-¾x + y = -2
Answer:
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