13.
[tex]x^2+x-20=(x+5)(x-4)[/tex]
Then, the zeros are x=-5 and x=4.
14.
[tex]x^2-4x-60=(x+6)(x-10)[/tex]
Then, the zeros are x=-6 and x=10.
15.
[tex]x^2-15x+50=(x-5)(x-10)[/tex]
Then the zeros are x=5 and x=10.
16.
[tex]x^2-x-72=(x+8)(x-7)[/tex]
Then the zeros are x=-8 and x=7.
17.
[tex]x^2+2x-48=(x+8)(x-6)[/tex]
Then the zeros are x=-8 and x=6.
18.
[tex]x^2-12x+36=(x-6)^2[/tex]
Then there is only one zero at x=6.
19.
[tex]x^2+32x+60=(x+30)(x+2)[/tex]
Then the zeros are x=-30 and x=-2.
20.
[tex]x^2-21x-100=(x+4)(x-25)[/tex]
Then the zeros are x=-4 and x=25.
