You would use the distributive property with the negative. So the second x becomes negative, but since the 7 is already negative it becomes positive. Think of it as if you put the two dashes together you can make a plus sign.
Volume of cylinder:
V = πr²h
The desired volume is 1 Liter = 1000 cm³
1000 = πr²h
h = 1000/πr²
Surface area of cylinder:
S.A = 2πr² + 2πr²h
We substitute the value of h from the first equation:
S.A = 2πr² + 2πr(1/πr²)
S.A = 2πr² + 2/r
Now, to minimize surface area, we differentiate the expression with respect to r and equate to 0.
0 = 4πr - 1000/r²
4πr³ - 1000 = 0
r = 4.3 cm
h = 17.2 cm
Answer:
She could have subtracted 19 from both sides. Hope this helps :)
Step-by-step explanation:
X²+bx=c
x=[-b+√(b²+4c)]/2
2x(x+5)=4
2x²+10x=4
x²+5x=2
x=[-5+√(5²+4*4)]/2
if b=-1/2 and c=-9/2
x= {1/2+√[(1/2)²+4*(-9/2)]}/2
