Question

Trying to solve the equation:
z^2+8z=-15

Answer 1

\(\normalsize\color{darkgreen}{ \rm z^2+8z=-15 }\)
` Way 1. `
Add 16 to both sides, and complete the square.
` Way 2. `
Add 15 to both sides and factor. HINT: \(\normalsize\color{darkgreen}{ \rm 8=5+3 }\)
` Way 3. `
Quadratic formula.

Answer 2

I prefer way 2

Answer 3

@hrassistant , are you there ?

Answer 4

yes

Answer 5

So try one of the ways... either one is fine, just that I suggest to do it the second way.

Answer 6

so I take the equation and add 15 to both sides leaving the one side with a zero

Answer 7

yes, exactly :)

Answer 8

so now I have z^2+8z+15=0

Answer 9

can I combine terms

Answer 10

You can not add anything in the equation, but you can factor it.

Answer 11

z(z+8)+15

Answer 12

No

Answer 13

\(\Large\color{darkgreen}{ (x+ \text{_})( x+ \text{_}) }\) fill in the blanks.

Answer 14

(z+4)(z+2)

Answer 15

oops

Answer 16

4 and 2 ? You are incorrect again.
Lets get back to factoring later, try to use the quadratic formula.

Answer 17

(z+5)(z+3)

Answer 18

Yes, ` (x+5)(x+3) ` is correct.

Answer 19

So this is what you/we are doing....

\(\Large\color{darkgreen}{ z^2+8z=-15 }\)

\(\Large\color{darkgreen}{ z^2+8z\color{red}{+15}=-15 \color{red}{+15} }\)

\(\Large\color{darkgreen}{ z^2+8z+15=0 }\)

\(\Large\color{darkgreen}{(z+3)(z+5)=0 }\)

Answer 20

thank you!!!

Answer 21

You welcome:)
IF you want to know I can show how to complete the square, but you don't have to worry about it if you don't want to.