Б) x^2-x = a

a^2-15a-100=0

D=15*15+4*100 = 625=25^2

a1 = (15+25)/2=20

a2 = (15-25)/2=-5

x^2-x=20, x^2-x-20=0, D=1+4*20=81 =9^2, x1=(1+9)/2=5, x2=(1-9)/2=-4

x^2-x=-5, x^2-x+5=0, D=1-4*5=-19<0

x=5 или x=-4

В)

3(x^2+x)^2 -10x^2 -10x=48

3(x^2+x)^2 -10(x^2+x)-48=0

x^2+x = a

3a^2-10a-48=0

D=10*10+4*3*48 = 100+576=676=26^2

a1 = (10+26)/6=6

a2 = (10-26)/6=-8/3

x^2+x=6, x^2+x-6=0, D=1+4*6=25 =5^2, x1=(-1+5)/2=2, x2=(-1-5)/2=-3

x^2+x=-8/3, x^2+x+8/3=0, D=1-4*8/3=<0

x=2 или x=-3