A) X^2-7x+12

D) X^2-2x-63

А) х²-7 х+12=0

а=1; b = - 7; с=12

D=b²-4ac = (-7) ²-4*1*12=49-48=1

√D=√1=1

x₁ = (-b-√D) / 2a = (7-1) / 2 = 3

x₂ = (-b+√D) / 2a = (7+1) / 2 = 4

d) D=4+252=256

√D=16

x₁ = (2-16) / 2 = - 7

x₂ = (2+16) / 2 = 9