X²-9≥0 U x≠4
(x-3)(x+3)≥0⇒x=3 U x=-3
+ _ +
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-3 3
x∈(-≈;-3) U (3;4) U (4;≈)
3a1+9d=15
a1+3d=5
(a1+2d)^2+(a1+4d)^2=58
(5-d)^2+(5+d)^2=58
25+d^2-10d+25+d^2+10d=58
50+2d^2=58
2d^2=8
d^2=4
d=2 , прогрессия возрастающая
a7=a1+6d=a1+3d+3d=5+3*2=11
1)(5a-10)/a²-4=5(a-2)/(a-2)(a+2)=5/a+2
2)(a²-2ab)/3a-6b=(a(a-2b))/(2(a-2b))=a/2
3) (a+3)³/5a²+15a=(a+3)³/(5a(a+3))=(a+3)²/5a
4)(m³-5m²n)/(mn²-5n)=(m²(m-5n))/(n²(m-5/n)
5)a²-6a+9/a²-9=((a-3)(a-3))/((a+3)(a-3))=(a-3)/(a+3)
6)a²-2a+1/a²-1=((a-1)(a-1))/((a+1)(a-1))=(a-1)/(a+1)