C because a is incorrect and so is b and d
Answer:
Eq: (x+a/2)²+(y+1)²=(a²-8)/4
Center: O(-a/2, -1)
Radius: r=0.5×sqrt(a²-8)
Mandatory: a>2×sqrt(2)
Step-by-step explanation:
The circle with center in O(xo,yo) and radius r has the equation:
(x-xo)²+(y-yo)²=r²
We have:
x²+y²+ax+2y+3=0
But: x²+ax=x²+2(a/2)x+a²/4-a²/4= (x+a/2)²-a²/4
And
y²+2y+3=y²+2y+1+2=(y+1)²+2
Replacing, we get:
(x+a/2)²-a²/4+(y+1)²+2=0
(x+a/2)²+(y+1)²=a²/4-2=(a²-8)/4
By visual inspection we note that:
- center of circle: O(-a/2, -1)
- radius: r=sqrt((a²-8)/4)=0.5×sqrt(a²-8). This means a²>8 or a>2×sqrt(2)
X/7 + 9 = 3
a number: x
a number divided by 7: x/7
sum of number divided by 7 and 9: x/7 + 9 (and means plus)
equals 3: x/7 + 9 = 3
Alright, lets get started.
Suppose first mechanic charges= x
So, second mechanic charges will be = 
(because total of their rates was 125)
first mechanic worked for 5 hours, and the second mechanic worked for 15 hours and together they charged a total of $1225
Means
Adding 10 x in both sides
Subtracting 1225 from both sides
Dividing 10 in both sides
x = 65
For second mecahnics rate = 125 - 65 = 60
Hence The mechanic who worked 5 hours charged $ 65 per hour, the one who worked 15 hours charged $ 60 per hour: Answer
Hope it will help :)
