Step 1. Simplify
7x^2 - 8x - 4 - 2x^2 + 3x + 5 + 5x^2 - 10x - 8
Step 2. Collect like terms
(7x^2 - 2x^2 + 5x^2) + (-8x + 3x - 10x) + (-4 + 5 - 8)
Step 3. Simplify
10x^2 - 15x - 7
That’s the correct answer
We need the radius to find the surface area. Since we have the circumference we can use that to find the radius.
C = 2πr
23 = 2(3.14)r
23 = 6.28r
23/6.28 = r
3.66 = r
Now use the radius to find the surface area.
SA = 4πr²
SA = 4(3.14)(3.66)²
SA = 168.33
Surface area is C. 168 cm²
Hope this helps :)
