Answer:
Step-by-step explanation:
1). x² - 10x + a²
By using the formula of (a - b)² = a² - 2ab + b²
x² - 2(5)x + a²
Therefore, for a perfect square of the expression a should be equal to 5.
Therefore, (x² - 10x + 25) will be the answer.
2). x² + 2ax + 36
= x² + 2(a)x + 6²
For a perfect square of the given expression value of a should be 6.
x² + 2(a)x + 6² = x² + 2(6)x + 6²
= (x + 6)²
Therefore, x² + 12x + 36 will be the answer.
3). 

To make this expression a perfect square,
a² = 
= 
Therefore, the missing number will be
.
Answer:
..... surface area = 16 km^2.
Answer:
1. not proportional because it's increasing in different values
2. proportional because the value is increasing equally
3. proportional because the values are increasing in equal amount
4. Proportional because it's increasing in equal amounts