ANSWERS:
2
−
4
−
2
1
x^{2}-4x-21
x2−4x−21
Grouping
1
Use the sum-product pattern
2
−
4
−
2
1
x^{2}{\color{#c92786}{-4x}}-21
x2−4x−21
2
+
3
−
7
−
2
1
x^{2}+{\color{#c92786}{3x}}{\color{#c92786}{-7x}}-21
x2+3x−7x−21
2
Common factor from the two pairs
3
Rewrite in factored form
Solution
(
−
7
)
(
+
3
)
