Please answer this questions step by step

(a) When a = 4 and b = -5,  a² + b² - a·b = 61

(b) When a = 4 and b = -5,  a³·b + a·b² = -220

(c)  

(d) When a = 4 and b = -5, (a + b)² - (a - b)² = 82

Step-by-step explanation:

The question relates to evaluation of expressions, given the values of the variables, "a" and "b"

Where;

a = 4 and b = -5

(a) For a² + b² - a·b, we have;

a² + b² - a·b = 4² + (-5)² - 4 × (-5) = 16 + 25 + 20 = 41 + 20 = 61

(b) For a³·b + a·b² we have;

a³·b + a·b² = 4³·(-5) + 4·(-5)² = 64 × (-5) + 4 × 25 = -320 + 100 = -220

(c) For , we have;

(d) For (a + b)² - (a - b)² we have;

(a + b)² - (a - b)² = (4 + (-5))² - (4 - (-5))² = (4 - 5)² - (4 + 5)² = (-1)² - 9² = 1 + 81 = 82

When a = 4 and b = -5, (a + b)² - (a - b)² = 82

step-by-step explanation:

12: 00 p.m. to 7: 00 p.m. is a total of 7 hours.

4: 00 p.m. to 7: 00 p.m. is a total of 3 hours.

this means that from 4: 00 p.m to 7: 00 p.m. this represents 3/7 of what was lost from 12: 00 p.m. to 7: 00 p.m.

after knowing this, after doing 11,600 - 6,800 = 4,800

4,800 represents 3/7 of what was lost for 7 hours.

we then divide 4,800 by 3 which gets 1,600.

because we know that 1,600 represents 1/7 of how much water was lost, we just have to multiply by 7, which gets 11,200.   after adding 11,200 to how much water was left at 7: 00 p.m. which was 6,800. 11,200 + 6,800 = 18,000

this means that the pool originally had 18,000 gallons in the pool.

you can also check your work by doing 18,000 - 4(1600), which becomes           1800 - 6400 which gets you 11,600.