The decay of 249 mg of an isotope is given by A=249e−0.015t , where t is time in years. Find the amount after 43 years.

A≈676.2

Step-by-step explanation:

1. Exponentially solve equation

A=249e-0.0015t as t = 43 years (Unless conversion to seconds)

A≈676.2

2. Solve graphically = intersect = (43, 676.2) x axis is time y axis is amount.

for the friend request.

when a figure, such as triangle (xyz) is reflected over the line y = x to create x'y'z' the x-coordinates and y-coordinates of the original image (pre-image) will be reversed for the image. (e.g., (x, y) > (y, x)) this means that the pre-image position of the x- and y-coordinates switch places which in turn provides a mirror like image of the original xyz.  

i notice that when i draw a line segment from x to x', that the points are parallel from each other -- they are exactly across from each other and do not intersect with any other points.  

yes, think i would see the same characteristic if you drew the line segment connecting y with the reflecting line and then y' with the reflecting line because of the essence of reflections. because it is a mirror image, each point was effected the same way which leads me to conclude that they same would apply to y and y'.