x1=(7+11)/18=1
x2=(7-11)/18=-2/9
2.5X=12
X=12/5
3.5X^2=45
X^2=9
X=±3
4.D=400-4*91=36=6^2
x1=(-20+6)/2=-7
x2=(-20-6)/2=-13
2
a+b=13
a=13-b
b(13-b)=36
-b^2+13b=36
b^2-13b+36=0
D=169-4*36=25=5^2
b1=(13+5)/2=9 a1=4
b2=(13-5)/2=4 a2=9
3 a=? b=13
a+b=-(-7)
a+13=7
a=-6
a*b=q
13*(-6)=-78
ответ:q=-78
