The product of 2x-3 and x+4 can be expressed as what

(2x - 3) * (x+4) =

2x*x + 2x*4 - 3*x - 3*4 =

2x^2 + 8x - 3x - 12 =

2x^2 + 5X - 12 =

a = 2; b = 5, c = - 12

Δ = b^2 - 4. a. c

Δ = 5^2 - 4.2. (-12)

Δ = 25 - 8. (-12)

Δ = 25 + 96

Δ = 121

x = - b±√Δ / 2. a

x = - 5±√121 / 2.2

x = - 5±11 / 4

x' = - 5-11 / 4 = - 16/4 = > x' = - 4

x" = - 5+11 / 4 = 6/4 (:2) = > x" = 3/2

Hope it cleared your doubt.