Tìm số nguyên x thỏa mãn: -210=(-1)+(-2)+(-3)+............+(-x+1)+(-x)
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tìm số nguyên x thỏa mãn : -210=(-1)+(-2)+(-3)+....+(-x+1)+(-x)
tìm số nguyên x thỏa mãn -210 = ( -1 ) + ( - 2 ) + ( - 3) + ...+ ( -x + 1 ) + ( - x )
tìm số nguyên x thỏa mãn -210 =(-1) +(-2)+(-3)+.. +(-x+1)+(x)
tìm số nguyên x thỏa mãn : -210=(-1)+(-2)+(-3)+....+(-x+1)+(-x)
-210 = (-1) + (-2) + (-3) + ... + (-x + 1) + (-x)
=> -210 = -(1 + 2 + 3 + ...+ x - 1 + x)
=> 210 = 1 + 2 + 3 + x - 1 + x
=> 210 = \(\frac{\left(x+1\right).x}{2}\)
=> 420 = (x + 1).x
=> 21 . 20 = (x + 1) . x
=> (20 + 1) . 20 = (x + 1) . x
=> x = 20
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x = 20 mình chắc chắn luôn
bạn gặp trong vòng 13 cua thi violympic đúng ko ?
nếu đúng mong bạn k cho^_^
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Tìm số nguyên x thỏa mãn : -210 = ( -1 ) + ( -2 ) + ( -3 ) + ....... + ( -x + 1 ) + ( -x ).
Trả lời:
Ta có: -210=(-1)+(-2)+(-3)+...+(-x+1)+(-x)
-210=-[1+2+3+...+(x-1)+x)]
-210=\(-\left[\frac{x\left(x+1\right)}{2}\right]\)
hay 210=\(\left[\frac{x\left(x+1\right)}{2}\right]\)
=> x(x+1)=210.2=420
=> 20.21=420 => x=20
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Tìm số nguyên x thỏa mãn:. 210=(-1)+(-2)+(-3)+...+(-x+1)+(-x)
Trả lời: ... ?
Tìm số nguyên x thỏa mãn: -210=(-1)+(-2)+(-3)+...+(-x+1)+(-x). Trả lời: x=
Tìm số nguyên x thỏa mãn -210=(-1)+(-2)+(-3)+...+(-x+10)+(-x). Tìm số đó
Tìm số nguyên thỏa mãn:.-210=-1+(-2)+(-3)+.........+(-x+1)+(-x)
Trả lời: X=