Hi Pablo,
I'm not sure I understand but I'll test tomorrow in high school.
With the file below, using what you offer, will the dimensions of my page be respected ?
\setuplayout
[header=\zeropoint,
headerdistance=\lineheight,
backspace=2cm,
width=middle,
topspace=\dimexpr 2cm-\headerheight-\headerdistance\relax,
footer=\lineheight,
height=middle]
\setupinteractionscreen[option=landscape]
\setuppagenumbering[alternative=,location=]
\definemixedcolumns
[MyColumns]
[
n=2,
separator=rule,
rulecolor=,
balance=yes,
]
\setupalign[verytolerant,stretch,hanging]
\starttext
\startMyColumns
\startformula
\startmathalignment[n=2,align={left,left}]
\NC P_1 + P_2 + \dots + P_{12} \NC = 400 + 400\times 1,05 + 400\times 1,05^2 + \dots + 400 \times 1,05^{11}\NR
\NC \NC = 400\times (1 + 1,05 + 1,05^2 + \dots + 1,05^{11})\NR
\NC \NC = 400\times \frac{1-1,05^{12}}{1-1,05}\approx 6\,367.\NR
\stopmathalignment
\stopformula
\dorecurse{6}{\input knuth}
\stopMyColumns
\stoptext