Answer:
6
Step-by-step explanation:
If the sum of the digits of a number is divisible by 9, then the number is divisible by 9.
So 6+7+8+5+Δ+4 = Δ + 30 has to be divisable by 9, and of course 0≤Δ≤9
36 is divisable by 9, so Δ has to be 6.
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Answer:
Domain: 
Range: ![(-\infty, 3]](https://tex.z-dn.net/?f=%28-%5Cinfty%2C%203%5D)
Decreases over: 
Step-by-step explanation:
Given
--- Missing from the question
Solving (a): The domain
To get the domain, the expression under the square root must not be negative.
In other words:

Solve for x


Hence, the domain is:

To get the range, we plot the values of the domain in the expression.











So, the range is: ![(-\infty, 3]](https://tex.z-dn.net/?f=%28-%5Cinfty%2C%203%5D)
To get the interval where the function increases or not, we simply plot the graph of f(x).
See attachment for graph.
From the attachment, it will be observed that the graph of f(x) continuously decreases from x = -1, and it never increased.
This implies that, the graph decreases over the interval 
(1 - 2x)⁴
(1 - 2x)(1 - 2x)(1 - 2x)(1 - 2x)
[1(1 - 2x) - 2x(1 - 2x)][1(1 - 2x) - 2x(1 - 2x)]
[1(1) - 1(2x) - 2x(1) - 2x(-2x)][1(1) - 1(2x) - 2x(1) - 2x(-2x)]
(1 - 2x - 2x + 4x²)(1 - 2x - 2x + 4x²)
(1 - 4x + 4x²)(1 - 4x + 4x²)
1(1 - 4x + 4x²) - 4x(1 - 4x + 4x²) + 4x²(1 - 4x + 4x²)
1(1) - 1(4x) + 1(4x²) - 4x(1) - 4x(-4x) - 4x(4x²) + 4x²(1) - 4x²(4x) + 4x²(4x²)
1 - 4x + 4x² - 4x + 16x² - 16x³ + 4x² - 16x³ + 16x⁴
1 - 4x - 4x + 4x² + 16x² + 4x² - 16x³ - 16x³ + 16x⁴
1 - 8x + 24x² - 32x³ + 16x⁴
Answer:
Step-by-step explanation:
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