Question

HELP
Solve by factoring.

5x^2+47x+56=0

Answer 1

use the ac method
5x56=280
find the factor of 280 that sum up to 47

Answer 2

hmm, im still confused :L

Answer 3

oh wait
is it 7 x 40

Answer 4

will any second degree poly can be written like a(x+b)(x+c)
the goal here is to a,b,c

Answer 5

but ac method don't worry about a just b and c

Answer 6

yes that is correct

Answer 7

40x7=280
and 40+7=47
good

Answer 8

now lets rewrite the equation \[5x^2+47x+56=5x^2+40x+7x+56=(5x^2+40)+(7x+56)\]

Answer 9

now what you can see is 5x^2and 40x have 5x in common

Answer 10

error in parenthesis i should have (5x^2+40x) not (5x^2+40)
forget x

Answer 11

and we can also see that 7x and 56 have 7 in common (common factor)
so we can now do this
\[=5x(x+8)+7(x+8)=(5x+7)(x+8)\]

Answer 12

so we got (5x+7)(x+8)

Answer 13

ohhhh , okay now i get it

Answer 14

alright thankyou!

Answer 15

you welcome

Answer 16

wait can we do one more equation?

Answer 17

7a^2 - a - 8 = 0