4= √([2d)/9.8] my teacher never taught us this please help

78.4

Step-by-step explanation:

4= √([2d)/9.8]

you square both sides to eliminate the square root so you get

4^2=√([2d)/9.8] ^2

16=2d/9.8

then you multiply both sides by 9.8 and you get

156.8=2d

then you divide both sides by 2 to leave d by itself and get

d=78.4

you can first factor out the n to get n(1+5). we know that 1+5 is 6, so we just have 6n.