The unit rate is -1/3.
In direct variation, y varies directly to x by a constant ratio k.
Its equation looks like this: y = kx ; where k stands for the constant ratio.
In the above equation. x = -3y, it should be converted to the proper equation. both sides must be transferred and its accompanying sign must be changed.
3y = -x
3y/3 = -x/3
y = (-1/3)x
where: y is the total value; -1/3 is the unit rate; and x is the number of units
The equation is y = 20(1.40)^x
where x is the number of days and y is the future amount after x days go by
The 1.40 is from the fact that 1+r = 1+0.40 = 1.40, where r is the decimal form of 40%, so r = 0.40
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Plug in x = 7 to get
y = 20(1.40)^x
y = 20(1.40)^7
y = 210.827008
y = 211
We round to the nearest whole number since it doesn't make much sense to have a fractional portion of an algae. After 7 days, there are about <u>211</u> algae.
When adding two negative numbers, add the absolute value of the numbers and keep the negative sign.
