7x^2 - 16x - 15 = 0
D = 256 + 420 = 676 = 26^2
x1 = ( 16 + 26)/14 = 42/14 = 3;
x2 = ( 16 - 26)/14 = - 10/14 = - 5/7
-2x ≤ -4 3x < 21
x≥ 2 x < 7
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x∈[2; 7)
x={2; 3; 4; 5; 6} - целые решения
<u>2+3+4+5+6 </u>= 20/5 = 4
5
Ответ: Г)4
(√x-√40)(√x+√40) = x-40, x>0
<span>2oc²-5с⁴=5c</span>²(4-c²)=5c²(2-c)(2+c)=0
c=0
c=2
c=-2