factor each term to see a GCF maybe
[tex]9x^2=3*3*x*x[/tex]
[tex]42x=2*3*7*x[/tex]
[tex]49=7*7[/tex]
no gcf
ok, hum
well, we see the first term might be √9 or 3 and the last must be √49 or 7
lets try (3x+7)(3x+7)
[tex]9x^2+21x+21x+49=9x^2+42x+49[/tex]
works
answer is (3x+7)(3x+7)
