1
{a1+a5=24⇒a1+a1+4d=24⇒2a1+4d=24⇒a1+2d=12/*(-2)⇒-2a1-4d=-24
{a2+a3=60⇒a1+d+a1+2d=60⇒2a1+3d=60
прибавим
-d=36
d=-36
a1-72=12
a1=72+12
a1=84
Sn=(2a1+d(n-1))*n/2
(168-36*(n-1))*n/2=60
(168-36n+36)*n=120
(204-36n)*n=120
36n²-204n+120=0
6n²-34n+20=0
D=1156-480=676
n=(34-26)/12=2/3 не удов усл
n=(34+26)/12=5
2
bn=b1*q^(n-1)
17*q^(n-1)=425
q^(n-1)=25⇒q^n=25q
Sn=b1*(q^n -1)/(q-1)
17*(q^n -1)/(q-1)=357
(q^n -1)/(q-1)=357:17
(q^n -1)/(q-1)=21
(25q-1)/(q-1)=21
25q-1=21q-21
25q-21q=-21+1
4q=-20
q=-5
(-5)^(n-1)=25
(-5)^(n-1)=(-5)²
n-1=2
n=3
3
√(22-x)-√(10-x)=2
ОДЗ
{22-x≥0⇒x≤22
{10-x≥0⇒x≤10
x∈(-∞;10]
возведем в квадрат
22-x+10-x-2√(220-32x+x²)=4
2√(220-32x+x²)=28-2x
√(220-32x+x²)=14-x
220-32x+x²=196-28x+x²
-28x+x²+32x-x²=220-196
4x=24
x=24:4
x=6