Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

$2t^4-11t^2-21$
Using $(a+b)(c+d)=ac+ad+bc+bd$ or the product of 2 binomials, the product of the given expression, $(2t^2+3)(t^2-7) ,$ is \begin{array}{l}\require{cancel} 2t^2(t^2)+2t^2(-7)+3(t^2)+3(-7) \\\\= 2t^4-14t^2+3t^2-21 \\\\= 2t^4-11t^2-21 .\end{array}