Check my work will give medals if you tell if this is right or ! let f(x)=x+5 and g(x)=x^2. find (g o f) (4) a. 9 < my answer b. 81 c. 20 d. 1 2. police can estimate the speed of a vehicle before the brakes are applied using the formula 0.75d=s^2/30.25, where s is the speed in miles per hour and d is the length of the vehicle's skid marks. what was the approximate speed of a vehicle that left skid marks measuring 140 feet? a. about 10 miles per hour < -- my answer b. about 75 miles per hour c. about 15 miles per hour d. about 56 miles per hour,

Since f(x)=(x+5) and g(x)=x^2, (g circle f)(x) means g(f(x)) which is composition. This tells us to substitute f(x) into g wherever there is an x. Here we want g(f(4)). First substitute 4 into f. THat is f(4)=4+5=9. THe we want g(f(4))=g(9). SUbstitute 9 into g which would be 9^2=81. The answer is 81. If .75d=s^2/30.25 and we know d is the length of the skid mark which here is 140, we substitute 140 in for d. 0.75*140=s^2/30.25 Multiply both sides by 30.25. s^2=105*30.25=3176.25 Take the square root of both sides and we get +/- sqrt 3176.25 But we only want the positive answer since we are talking speed. So s=56.358 which is about 56 miles per hour.

1. The answer is letter B. 81
Since f(x)=(x+5) and g(x)=x^2, 
First substitute 4 into f which is
 f(4)=4+5=9.
then g(f(4))=g(9). 
 9^2=81

2.The answer is D. about 56 miles per hour
75d=s^2/30.25
given: d= 140
so 0.75*140=s^2/30.25
 s^2=105*30.25=3176.25 
= +/- sqrt 3176.25 
 s=56.358
=56 miles per hour.

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