15: (k+5) (k-1)= [tex]k ^{2} +4k-5[/tex]
16: (x-4) (x+8)= [tex] x^{2} +4x-32[/tex]
17: (q-3) (q-4)=[tex] q^{2} -7q+12[/tex]
18: (z-5) (z-9)=[tex] z^{2} -14z+45[/tex]
19: (t+2) (2t+1)=[tex]2 t^{2} +5t+2[/tex]
20: (5v-3) (2v+4)=[tex]10 v^{2} +14v-12 [/tex]
21: (9-r) (2-3r)=[tex]3r ^{2} -29r+18[/tex]
