(2x2 − x) + (x2 + 3x − 1)
1 answer:
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Answer:
4 mph
Step-by-step explanation:
The average speed of an object is given by the total distance covered by the time taken:
where
d is the total distance covered
t is the time taken
in the first part, the person runs for 0.4 hours at a speed of 7 mph, so the distance covered in the 1st part is
Then the distance covered in the second part is , so the total distance is
(1)
The total time elapsed is 0.4 hours (first part) + 0.8 hours (second part), so
So we can write the average speed as
(1)
We want the average speed to be 5 mph,
v = 5 mph
Therefore we can rearrange eq.(1) to find d2:
And therefore, the speed in the second part must be
Here's our equation:
Factor out the left side
(-2x - 3) - 4 = 3/4 (-8x - 12)
Simplify
-2x - 7 = 3/4 (-8x - 12)
Factor out the right side
-2x - 7 = -6x - 9
Add 7
-2x = 6x - 2
Add 6x to isolate the variable
4x = -2
Divide by 4
x = - 1/2
Here is how I simplified both sides initially. I'll only be showing the right side because this is a LOT of typing.
Begin with 3/4 (-8x - 12)
Use rule to multiply
3(-8x-12)/4
Factor 3(-8x-12)
(-8x - 12) = (-4 * 2x - 4 * 3)
Simplify (-4 * 2x - 4 * 3)
-3 * 4 (2x+3)
- 12 (2x + 3)
Now that we've factored 3/4 (-8x - 12), we're left with- 12 (2x + 3)/4.
12/4 =3, giving us -3(2x + 3)
Distribute and simplify, then you're done.