Question

Solve to equation, 2x^2-x-1=0, using the quadratic formula.

A.x=-1 or x=-1/2
B.x=-1 or x=2
C.x=1 or x=-1/2
D.x=1 or x=1/2

Answer 1

C

for the quadratic 2x² - x - 1 = 0 ← in standard form

with a = 2, b = - 1 and c = - 1 , then

x = (1 ± √( 1 + 8 )) / 4 ← quadratic formula

= ( 1 ±
`√(9)`) / 4

= ( 1 ± 3 ) / 4

x =
`(1+3)/(4)` or x =
`(1-3)/(4)`

x =
`(4)/(4)` = 1 or x =
`(-2)/(4)` = -
`(1)/(2)`