8 / ( X + 4 ) + 16 / ( X - 4 ) = 4/3
24*( X - 4) + 48*( X + 4) = 4*(X^2 - 16)
24X - 96 + 48X + 192 = 4X^2 - 64
4X^2 - 72X - 160 = 0
4 * ( X^2 - 18X - 40) = 0
D = 324 + 160 = 484 ; √ D = 22
X1 = ( 18 + 22) : 2 = 20
X2 = ( - 4) : 2 = ( - 2 )
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X^2 - 16 ≠ 0
X^2 ≠ 16
X ≠ 4
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Ответ 20 км/час
Решение
<span>2х</span>²<span>+6х=0
2x*(x + 3) = 0
x</span>₁<span> = 0
x + 3 = 0
x</span>₂<span> = - 3</span>
Sn=0,5*(a1+an)*n;
85=0,5*(a1+22)*10;
a1+22=85:5;
a1=17-22=-5;
a10=a1+d(10-1);
22=-5+9d;
9d=22+5;
d=27:9=3;
ответ: -5; 3