Question

I need some homework help?

Use the quadratic formula to solve 10x2 - 30x – 100 = 0.

A. x = -2 or x = 5

B. x = -5 or x = 2

C. x = 2 or x = -4

D. x = -4 or x = -2

Answer 1

Do you know the quadratic formula?

Answer 2

no

Answer 3

that's why im asking what the answer is

Answer 4

\[\huge\color{blue}{ x=~~\frac{-b±\sqrt{b^2-4(a)(c)} }{2a} } \]

Answer 5

Are you familiar with this formula in blue ?

Answer 6

I've seen it before, I'm just not sure how to do it

Answer 7

alright, the a b c there are numbers.

the standard form of the equation is
\[\huge\color{blue}{ ax^2+bx+c=0 } \]
compare your equation to this form and tell me what the "a" b" and "c" in your equation are

Answer 8

\[ \huge\color{blue}{ \color{red} { 10 } x^2\color{red} { -30 } x\color{red} { -100 } =0 } \]

can you tell me the A B C now ?

Answer 9

would a be 10 and 30 be b and 100 be c? I'm confused still

Answer 10

Yeah, exactly ! now you need to plug them in (that's all) !

Answer 11

\[\color{purple}{ x=~~\frac{-(-30)±\sqrt{(-30)^2-4(10)(-100)} }{2(10)} } \]
\[\color{purple}{ x=~~\frac{+30±\sqrt{(-30)^2-(-4000)} }{2(10)} } \]
\[\color{purple}{ x=~~\frac{+30±\sqrt{900+4000} }{2(10)} } \]
\[\color{purple}{ x=~~\frac{+30±\sqrt{4900} }{20} } \]
\[\color{purple}{ x=~~\frac{+30±70 }{20} } \]
\[\color{brown}{ x=~5~~~~~or~~~~~ -2 } \]

Answer 12

See how I am doing this ?

Answer 13

Yes i see i think. It's just the + or - symbols really confuse me..I never learned how to do that

Answer 14

this is just because of a square root.

b/c you know that \[\sqrt{49}=+7~~~~or~~~-7\]

Answer 15

But from what I got from doing all of that I got x = -2 or x = 5

Answer 16

and that makes much more sense now

Answer 17

Yup ! Nice to hear that. Good luck !

Answer 18

Thank you!

Answer 19

np