Answer: A
Step-by-step explanation:
2x²-2x-9=0
this is a quadratic equation so we will use the quadratic formula .
Δ= b²-4*a*c
- b= -2
- a= 2
- c= -9
let's calculate Δ to khow how many solutions this equations have .
Δ= (-2)²-4*2*(-9)
= 76
we notice that 76>0
so this equation has two solutions : (-b-√76)/4 and (-b+√76)/4
- let's calculte the values :
- (-b-√76)/4=
(-b+√76)/4=
the trick here is to notice that :
=
=
= 2
Now we will simplify Δ by factoring by 2
=
so the answer is a .