11.0k views
3 votes
Factor the expression. 21x^2 + 43x + 20

(7x – 5)(3x – 4)

(7x + 5)(3x + 4)

(7x – 5)(3x + 4)

(7x + 5)(3x – 4)

User Kixoka
by
5.8k points

2 Answers

6 votes
Hello,


21x^2 + 43x + 20\\ =21x^2+28x+15x+20\\ =7x(3x+4)+5(3x+4)\\ =(3x+4)(7x+5)\\ Answer B
User Terje Dahl
by
5.3k points
6 votes
Each choice has 7x and 3x which multiply to 21x^2.
The original trinomial has positive 20 and positive 43, so all factors of 21 and of 20 must be positive.
Only choice B has all positive terms, so choice B must be the answer.
User Nikasv
by
5.9k points