Find ‘x’

Find x if 5=2x^2+15x+10

right answer

x=384??

Let me make a better one

-12, -15 , -8, 21 , x

Hint: It contains x³ somewhere in the main formula which you use to calculate the other sentences.

Now, it's fully solvable

It also needs a paper and pen to write, not solvable just by seeing

Not true

Level 3 sequences can be ascending , then descending, then again ascending.

That's why -12 decreased to -15 then again increased to -8

and after that point all the next sequences are gonna be increasing

let me do more hint:

an = 2n³ -7n² + cn + d

66

The answer was 84 , I made it too hard actually

the fully formula was

an = 2n³ - 7n² + 4n - 11

Let me give an easy one

2, 5, 10, 17, 26 , x

Yes, correct.