Step-by-step explanation:
(a-b)^2=(a^2-2*a*b+b^2)
4*(x^2-2x+1)-9=4x^2-8x+4-9=4x^2-8x-5
if you have to calculate the Δ
there is it: 4x^2-8x-5=0
Δ=b^2-4*a*c=64-4*4*(-5)=64+80=144
[tex]x_{1,2}=[/tex]-b±Δ/2*a=8±12/8=
[tex]x_{1}[/tex]=8+12/8=20/8|:4=5/2
[tex]x_{2}[/tex]=8-12/8=-4/8|:4=-1/2
