The equation would be y=-6x/5 +19 I think
One approach that might be a great help would be if you would look
at the choices ... those things at the bottom of the question that you
didn't give us.
-- One leg is 3 times the length of the other leg.
-- Any right triangle that has one leg three times as long as the other
leg is similar to this triangle.
I'll bet that if you look through the choices, you'll find one there.
I will explain you and pair two of the equations as an example to you. Then, you must pair the others.
1) Two circles are concentric if they have the same center and different radii.
2) The equation of a circle with center xc, yc, and radius r is:
(x - xc)^2 + (y - yc)^2 = r^2.
So, if you have that equation you can inmediately tell the coordinates of the center and the radius of the circle.
3) You can transform the equations given in your picture to the form (x -xc)^2 + (y -yc)^2 = r2 by completing squares.
Example:
Equation: 3x^2 + 3y^2 + 12x - 6y - 21 = 0
rearrange: 3x^2 + 12x + 3y^2 - 6y = 21
extract common factor 3: 3 (x^2 + 4x) + 3(y^2 -2y) = 3*7
=> (x^2 + 4x) + (y^2 - 2y) = 7
complete squares: (x + 2)^2 - 4 + (y - 1)^2 - 1 = 7
=> (x + 2)^2 + (y - 1)^2 = 12 => center = (-2,1), r = √12.
equation: 4x^2 + 4y^2 + 16x - 8y - 308 = 0
rearrange: 4x^2 + 16x + 4y^2 - 8y = 308
common factor 4: 4 (x^2 + 4x) + 4(y^2 -8y) = 4*77
=> (x^2 + 4x) + (y^2 - 2y) = 77
complete squares: (x + 2)^2 - 4 + (y - 1)^2 - 1 = 77
=> (x + 2)^2 + (y - 1)^2 = 82 => center = (-2,1), r = √82
Therefore, you conclude that these two circumferences have the same center and differet r, so they are concentric.
Answer:
A
Step-by-step explanation:
The first answer is correct because we have a decay factor.
The sample is losing mass, so the number that is being multiplied by a power of x must be less than 1.
If the second answer were used, then the sample would be gaining mass.
Think of this as (1/5)x - 4 = -75, where x is the number that we are trying to figure out. To figure this out, we want to get x by itself, so we can go:
(1/5)x=-71
x=-71*5
x=-355
So your number is -355
