Question 443671
Adding.
{{{(sn-4n^2+7)+(7n^2+5n-6)}}}
Assuming "sn" is really 2n, and that each = 0.
Reorganize the first equation to align the elements.
{{{2n-4n^2+7 = 0}}}
{{{-4n^2 +2n + 7 = 0}}}
Add
{{{-4n^2 +2n + 7 = 0}}}
{{{7n^2 + 5n -6 = 0}}}
{{{3n^2 + 7n + 1 = 0}}}
.
Subtracting
{{{7y^3+4y^2-5y+3 = 0}}}
{{{8y^3-4y^2-2y+2 = 0}}}
{{{-y^3 +8y^2 -3y + 1 = 0}}}
.
Done