a)(2x-3) (2x+3)=(x+5)²-9 4x²-9=x²+10x+25-9 4x²=x²+10x+25 3x²-10x-25=0 Δ=(-10)²-4*3*(-25)=100+300=400 √Δ=20 x1=10+20/6=30/6=5 x2=10-20/6=-10/6=-1 i 2/3 b)x²-(3x-1)²=56x-43 x²-9x²+6x-1=56x-43 -8x²+6x-1=56x-43 -8x²-50x+42=0 Δ=(-50)²-4*(-8)*42=2500+1344=3844 √Δ=62 x1=50+60/-16=110/-16=-6 i 7.8 x2=50-60/-16=-10/-16=5/8 c)3(x+1)(x-2)=2x²-x-7 3(x²-2x+x-2)=2x²-x-7 3(x²-x-2)=2x²-x-7 3x²-3x-6=2x²-x-7 x²-2x+1=0 Δ=(-2)²-4*1*1=4-4=0 x=3/6=1/2 d)17-5x=6x²+(x-x)² 17-5x=6x²+x²-2x²+x² 17-5x=6x² -6x²-5x+17=0 Δ=(-5)²-4*(-6)*17=25+408=433 √Δ=√433 x1=5+√433/-12 x2=5-√433/-12 e)11-14x=(2x+1)² 11-14x=4x²+4x+1 -4x²-18x+10=0 Δ=(-18)²-4*(-4)*10=324+160=484 √Δ=22 x1=18+22/-8=40/-8=-5 x2=18-22/-8=-4/-8=1/2 f)6x²=x+1 6x²-x-1=0 Δ=(-1)²-4*6*(-1)-1+24=25 √Δ=5 x1=1+5/12=6/12=1/2 x2=1-4/12=-3/12=-1/4 g)5x²=2-9x 5x²+9x-2=0 Δ=9²-4*5*(-2)=81+40=121 √Δ=11 x1=-9-11/10=-20/10=-2 x2=-9+11/10=2/10=1/5 ;))
