Answer:

Step-by-step explanation:
Greatest multiplier of 4 that is less than 21 is 5 (4 x 5 = 20)
Put the remaining number as the numerator (21 - 20 = 1)
The method you should chose is the quadratic formula
Answer: D
Step-by-step explanation: Using pemdas parentheses is always first so the answer is D.
Answer:

Step-by-step explanation:
In this problem we have a exponential function of the form

where
f(x) is the remaining mass of the element in grams
x is the time in minutes
a is the initial value (y-intercept of the exponential function)
b is the base
r is the rate

In this problem we have

---> is negative because is a decay's rate

substitute
The exponential function is equal to

For x=15 minutes
substitute in the function


Answer:
y=(-5/3)x+29
Step-by-step explanation:
we will use the base formula y=mx+b
In order to be perpendicular, the slope must be the flipped fraction and have the opposite sign, so our m is (-5/3)
y=(-5/3)x+b
You can plug in the (9,14) point in order to find the b
14=(-5/3)(9)+b
14=(-45/3)+b
14=(-15)+b
14+15=b
29=b
and so altogether our equation is y=(-5/3)x+29