If $5x^6-9x^2+1=(p{x}^4+q{x}^3+r{x}^2+sx+t)(a{x}^2+bx+c)$, then the value of $ap$ is

$(p{x}^4+q{x}^3+r{x}^2+sx+t)(a{x}^2+bx+c)$

By multiplying $x^4$ coefficient in $p{x}^4+q{x}^3+r{x}^2+sx+t$ and $x^2$ coefficient  in $a{x}^2+bx+c$  we get $ap{x}^6$

$5x^6=ap{x}^6$

$ap=5$