Answer:
15x²
Step-by-step explanation:
Given
f(x) = 5x² , then
3f(x) = 3 × 5x² = 15x²
Answer:
y = -16
Step-by-step explanation:
First lets handle the fractional y's:

This can be reduced down to 2y. That is easier to work with. Next we will rewrite the equation using or new value for y:
35 + 2y = 3
Subtract 35 from both sides:
2y = -32
Next, divide both sides by 2
y = -16
Check our answer:
35 + 
35 -40 + 8 = 3
-5 + 8 = 3
3 = 3
If every minute 3 poles past and poles are 1/4 mile (0.25 mile) apart;
3x0.25 = 0.75
Train moves 0.75 mile/per minute
If you want the train's speed per hour, then;
x = 60x0.75
x= 45miles per hour is the speed of the train