2x+90=7x
2x-7x=-90
-5x=-90
x=-90:(-5)
x=+18
<span><u>lim(x→1) [(∛x-1) / (√x-1)]</u></span>
x^1/3-1 = (x^1/6)²-1² =(x^1/6-1)(x^1/6+1)
x^1/2-1 = (x^1/6)³-1³ = (x^1/6-1)(x^2/6+x^1/6+1)
(x^1/6-1)(x^1/6+1):(x^1/6-1)(x^1/3+x^1/6+1)=
=(x^1/6+1)/(x^1/3+x^1/6+1)
lim(x^1/6+1)/(x^1/3+x^1/6+1) = (1+1)/(1+1+1) = 2/3
x->1
5/8+3/8=1
1/8+7/8=1
3/5+2/5=1
4/5+1/5=1
==================
1 4/7+3/7=2
8/7+6/7 =2
1/4+1 3/4=2
5/4+ 3/4 =2
==================
3/2+1 1/2=3
1 4/6+8/6=3
1 1/6+1 5/6=3
2 1/2+1/2=3
1/5кг-200г, 4/5кг-800г, 3/10кг - 300г, 1/4кг -250г