51) Rewrite the formula for the circumference of a circle C=2 /pi "r" in terms of its diameter "d". Please show your working :)
1 answer:
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One
<em><u>Slope</u></em>
The general slope intercept equation for a line is
y = mx + b
If you are told outright what the slope is then you can write m = slope in this case - 3
So you have so far is y = -3x + b. Now you use the point to get the y intercept.
(2,5) means that when x = 2, y = 5. that allows you to solve for b
<em><u>Y intercept</u></em>
When x = 2, y = 5. Substitute that into the general equation with the slope.
5 = -3x + b Put 2 in for x
5 = -3 * 2 + b Multiply -3 * 2
5 = - 6 + b Add 6 to both sides
5 + 6 = b
11 = b
Answer
y = -3x + 11
Two
This question is a little harder. You have to find the slope.
<em><u>Slope Formula</u></em>
<em><u>Givens</u></em>
Points (2, -1), (-6, - 5)
y2 = -1 ; y1 = -5; x2 = 2; x1 = -6
<em><u>Solve</u></em>
m = (-1 - - 5)/(2 - - 6) = (-1 + 5)(2 + 6) = 4/8 = 1/2
Now find the y intercept. Use either one of the given points
(2,-1) when x = 2, y = - 1
y = 1/2 x + b Show what you have so far. Put in x = 2 for x and y = - 1 for y
-1 = 1/2(2) + b Multiply 2*1/2
-1 = 1 + b Subtract 1 from both sides.
-1 -1 = b
- 2 = b
Answer
y = (1/2)x - 2 which is D