2а(3а-5b) - 3a(2a-b) = 2a*3a +2a*(-5b) - 3a*2a -3a*(-b)=
= 6a² - 10ab -6a² + 3ab = (6a² -6a²) + (-10ab + 3ab)=
= - 7ab
-12b(1/4 - a) - 6a(2b - 1/3) =
= - 12b/4 - 12b * (-a) - 6a*2b - 6a/(-3) =
= - 3b + 12ab - 12ab + 2a =
= - 3b + 2a =
= 2a - 3b
при а= - 0,7 ; b=2
2*(-0,7) - 3*2 = - 1,4 - 6 = - (1,4 + 6,0) = - 7,4
(a*b)^2=a^2*b^2
1/5^2*sqrt(10)^2=1/25*10=10/25=2/5=0,4
1. х2-8х+12=0
D=(-8)^2-4*1*12=64-48=16 D>0
x1=8+4/2=12/2=6
x2=8-4/2=4/2=2
2. 5x2+3x+7=0
D=3^2-4*5*7=9-140=-131 D<0
решения нет
3. х2-6х+9=0
D=(-6)^2-4*1*9=36-36=0 D=0
x1,2=6+-0/2=+-3
4. x2-2x-3=0
D=(-2)^2-4*1*(-3)=4+12=16 D>0
x1=2+4/2=6/2=3
x2=2-4/2=-2/2=-1
5. 15-2x-x2=0
-x2-2x+15=0
D=(-2)^2-4*(-1)*15=4+60=64 D>0
x1=2+8/-2=10/-2=-5
x2=2-8/-2=-6/-2=3
6. x2+12x+36=0
D=12^2-4*1*36=144-144=0 D=0
x1,2=-12+-0/2=+-6
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