The length will be 3 because of the altitude
Hello!
You can only add variables with the same base and exponent
8u^3 + 4u^3 = 12u^3
8u^2 + 0 = 8u^2
0 + -6u = -6u
6 + 3 = 9
Put the sums together
12u^3 + 8u^2 - 6u + 9
The answer is

Hope this helps!
a) This part is already complete I think..
b) This is a cuboid and lateral surface area of cuboid is: 2(lb +bh + hl)
= 2( 10 × 3 + 3 × 7 + 7 × 10)
= 2(30 + 21 + 70)
= 2 × 121 = 242 cm²
Now, the area of top & bottom: lb
= 2 × 10 × 3
= 60 cm²
Neglecting the top & bottom surface area of cuboid:
= 242 - 60
= 180 cm²
c) The total surface area us 242.. I have already done that part above...
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If i have done something wrong.. please lemme know :)
I belive there is none because it lands on the origin for y.