SOLUTION: when you are finding the surface area of a rectangular prism and you hav to find the polynomial in simplified form how do you get the answer? Because on the rectangular prism- the

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: when you are finding the surface area of a rectangular prism and you hav to find the polynomial in simplified form how do you get the answer? Because on the rectangular prism- the       Log On


   

Question 2352: when you are finding the surface area of a rectangular prism and you hav to find the polynomial in simplified form how do you get the answer? Because on the rectangular prism- the length and width is x+5 and the height is 3x-1 and i got 66x+-10 +12x squared and i think i did something wrong but i cant find out where? Pllleaase help asap, thankss!
Answer by longjonsilver(2297) About Me  (Show Source):
You can put this solution on YOUR website!
surface area...6 faces, 2 of each combination...
2((x+5)(x+5)) + 2((x+5)(3x-1)) + 2((x+5)(3x-1))
= 2((x+5)(x+5)) + 4((x+5)(3x-1))
= 2(x%5E2+%2B+10x+%2B+25) + 4(3x%5E2+%2B+14x+-5)
= 2x%5E2+%2B+20+x+%2B+50+%2B+12x%5E2+%2B+56x+-+20
so 14x%5E2+%2B+76x+%2B+30= 0
7x%5E2+%2B+38x+%2B+15+=+0
(7x + 3)(x + 5) = 0
so 7x+3=0 OR x+5=0
so, x=-3/7 or x=-5
jon