201k views
4 votes
2x^2-3x-9 please help

2 Answers

6 votes
so factor

if you have ax^2+bx+c then to factor find
x+y=b
xy=ac
so

a=2
b-03
c=-9
2 times -9=-18

factor -18
-1,18
-2, 9
-3, 6


now add and find the one that adds to -3


-1+18=17
-2+9=7
-3+ 6=3, could work, if signs are reversed

so the numbers are -6 and 3

split -3 up
2x^2-6x+3x-9
group
(2x^2-6x)+(3x-9)
undistribute
(2x)(x-3)+(3)(x-3)
reverse distributive property
ab+ac=a(b+c)
(2x+3)(x-3)


so we can't do anything else because it isn't an equation so it has non meaning

if it does equal zero then
xy=0 then x and/or y=0 so

(2x+3)(x-3)=0 so
2x+3=0 and x-3=0 so

2x+3=0
subtract 3 from both sides
2x=-3
divide by 2
x=-1.5

x-3=0
add 3 to both sides
x=3



x=-1.5 or 3

User Helmi
by
7.9k points
5 votes
Im assuming you mean 2x^2-3x-9=0 ?
If so, you have to factorise the equation
(2x-3) (x+3) = 0

2x - 3 = 0
2x = 3
x = 1.5

x + 3 = 0
x = -3

x is either 1.5 or -3

User Courage
by
7.9k points

No related questions found

Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.

9.4m questions

12.2m answers

Categories