Question

Solve. 2x2 - x = 15

x = 5 over 2 and x = 7
x = 7 over 2 and x = -1
x = 3 and x = - 5 over 2
x = 3 and x = 1

Answer 1

i'm not sure if i understand what 2x2 means

Answer 2

2 times 2?

Answer 3

ohh i get it. 2x^2-x=15 ?

Answer 4

just let me know if that is correct.

Answer 5

2x^2-x=15

2x^2-x-15 = 0

that's in the form ax^2 + bx + c = 0

so

a = 2
b = -1
c = -15

Plug those into the quadratic formula

\[\Large x=\frac{-b \pm \sqrt{b^2-4ac}}{2a}\]

Answer 6

\[1 \pm \sqrt{4 - 4(2)(-15)} \div 4\]

Answer 7

you get it..?

Answer 8

see the formula again...1st term in bracket is b...and b=-1 so b^2 =1 not =4..??

Answer 9

oh oops heehe

Answer 10

\[\Large x=\frac{-b \pm \sqrt{b^2-4ac}}{2a}\]

\[\Large x=\frac{-(-1) \pm \sqrt{(-1)^2-4(2)(-15)}}{2(2)}\]

\[\Large x=\frac{1 \pm \sqrt{1-(-120)}}{4}\]

\[\Large x=\frac{1 \pm \sqrt{121}}{4}\]

I'll let you finish up

Answer 11

idk how to simplify that? do you add 1 to 121? do you divide it all by 4??

Answer 12

first you have to take the square root of 121

Answer 13

its 11

Answer 14

So we have

\[\Large x=\frac{1 \pm 11}{4}\]

which breaks down into these two equations

\[\Large x=\frac{1 + 11}{4} \text{ or } x=\frac{1 - 11}{4}\]

Answer 15

do you see how to go from here?

Answer 16

yes thank you:)

Answer 17

alright great

Answer 18

wait no i dont know which answer it is :(

Answer 19

\[\Large x=\frac{1 + 11}{4}=???\]

Answer 20

3

Answer 21

\[\Large x=\frac{1 - 11}{4} = ???\]

Answer 22

OHHHHH

Answer 23

what's that equal to