Ta có :
`M(-2) = (-2)^3 + (-2)^2 + a.(-2) -5`
` => M(-2) = -8 + 4 - 2a -5`
`=> M(-2) = -9 - 2a`
`N(1) = -2.1^2 + 2.a.1 - 100`
`=> N(1) = -2 + 2a - 100`
`=> N(1) = 2a - 102`
Vì `M(-2) = N(1)` nên :
`-9-2a = 2a -102`
`=> -2a - 2a = -102 + 9`
`=> -4a = -93`
`=> a = 23,25`
Vậy `a=23,25`