Quadratic formula???

Question

Can someone help me with these two? I can't get them at all.

Solve the equation using quadratic formula:

1. 0 = x^2 + x - 20

2. 0 = x^2 - 5x + 6

Thanks!!!

Answer 1

Question 1
x = [- 1 ± √81] / 2
x = 8/2 , x = - 10/2
x = 4 , x = - 5

Question 2
x = [5 ± √1] / 2
x = 6/2 , x = 4/2
x = 3 , x = 2

NB Both questions could have been done by factorising.

Answer 2

1 is 3 and 2 is 2.

Answer 3

I'll just do the second one.

x^2 - 5x + 6 = 2 means
x^2 - 5x + 4 = 0
Now use the formula

x = (5 +/- 3) / 2
= 1, 4

Answer 4

wen u have these kinda problems i always ask myself, "what adds to the middle term and multiplys to the last term?" and u always carry down the first sign, not the second. so for number one u would get (x+5)(x-4), then u would set them both equal to 0 and solve for x. then u will get x= -5 and x= +4. you would choose 5 and -4 because 5*-4=-20 and 5+-4=1(or just x). follow so far?

as for the second, u would pretty much follow the same procedure.

1.ask yourself, what adds up to the middle term but multiplys to the last?
2. "double bubble"(a little term i like to use, also known as just doing this ( )( )
3. set ur final terms equal to zero, and get x.

so for number 2, start off by bringing the FIRST sign down(remember, only the first sign never the second)

so u would get so far:

(x-3)(x-2)

i chose -3 and -2 because -3+-2=-5 and -3*-2=6

now, set them equal to zero and solve for x

x-3=0
x-2=0

ur final answers are

x=3
x=2

Answer 5

and the first:

x = [-b +/- sqrt(b^2 - 4ac) ]/ 2a

a = 1, b = 1, c = -20

so

x = -1 +/- sqrt(1 - 4(-20))/ 2 = -1 +/- sqrt(81)/2

x = (-1 +/- 9 )/ 2

x = 4, -5