Question

Factor completely: 9x2 + 42x + 49

Answer 1

Any ideas to start off?

Answer 2

no idea :/ people have tried and tried to show me. But I never really get what their doing.

Answer 3

*they're

Answer 4

Ok. We start of by multiplying the first coefficient 9 by the last term 49 to get 441

Answer 5

Now we need to find two numbers that both multiply to 441 AND add to 42

Any ideas what those numbers could be?

Answer 6

Not off the top of my head.

Answer 7

Well it turns out that 21 and 21 multiply to 441 AND add to 42

Answer 8

(3x+7)(3x+7)

Answer 9

So this means that 42x breaks into 21x+21x


So

9x^2 + 42x + 49

then becomes

9x^2 + 21x+21x + 49

Answer 10

From here, you factor 9x^2 + 21x+21x + 49 by grouping

Answer 11

(3x+7)^2

Answer 12

Do you know how to do that?