Which expressions represent exponential decay? Check all that apply.

A. 900(0.05)t
B. 700(0.9)x
C. 53(1.75)(0.3)x
D. 90(1.2)t
E. .300(2.4)(1.2)y
F. 2x2 + 9
G. 18 – 3y

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expressions which represent exponential decay:

A. 900(0.05)^t

B. 700(0.9)^x

Step-by-step explanation:

Exponential decay functions has the next form:

y = ab^x

where b < 1

A. 900(0.05)^t , a = 900, b = 0.05, the variable is t instead of x. 0.05 < 1, then it represents exponential decay

B. 700(0.9)^x , a = 700, b = 0.9 < 1, then it represents exponential decay

C. 53(1.75)^(0.3x) =  53(1.75)^(0.3)(1.75)^x, a =  53(1.75)^(0.3), b = 1.75 > 1, then it doesn't represent exponential decay

D. 90(1.2)^t, a = 90, b = 1.2 > 1,  then it doesn't represent exponential decay. (the variable is t instead of x)

E. .300(2.4)^(1.2y)  = 300(2.4)^(1.2)(2.4)^y, a = 300(2.4)^(1.2),  b = 2.4 > 1, then it doesn't represent exponential decay. (the variable is y instead of x)

F. 2x² + 9 , this is a quadratic function,  then it doesn't represent exponential decay.

G. 18 – 3y, this is a linear function,  then it doesn't represent exponential decay.

walter needs to make at least 5 more cookies but no more than 40. 5 ≤ x ≤ 40

step-by-step explanation:

20 ≤ x + 15 ≤ 55

subtract 15 from all parts

20-15 ≤ x + 15-15 ≤ 55-15

5 ≤ x ≤ 40

this means how many more cookies he has to make

walter needs to make at least 5 more cookies, but no more than 40 cookies; 5 ≤ x ≤ 40

step-by-step explanation: