Question

Subpunctele a și b va rog dau coroana

Answer 1

Răspuns:

Explicație pas cu pas:

a) 0,1111x=4-0,667

0,1111x=3,333

x=3,333/0,1111

x=30

b) x(1+2+ .... +20)x=100x-(-1+4-27+256)

1+2+ .... +20 = [n(n+1)]/2   - suma Gauss

1+2+ ... +20 = 20×21/2=210

210x=100x-(260-28)

210x-100x=-232

110x=-232

x=-232/110 = simplificăm cu 2

x=-116/55

Answer 2

Explicație pas cu pas:

a)

$0.1x + 0.01x + 0.001x + 0.0001x = {2}^{2} - 0.667 \\ (0.1 + 0.01 + 0.001 + 0.0001) = 4 - 0.667 \\ 0.1111x= 3.333 \implies \bf x = 30$

b)

$x + 2x + 3x + ... + 20x = 100x - ( {( - 1 )}^{1} + ( { - 2})^{2} + ( { - 3})^{3} + ( { - 4})^{4})$

$(1 + 2 + 3 + ... + 20)x = 100x - ( - 1 + 4 - 27 + 256)$

$\frac{20 \cdot 21}{2} x = 100x - 232$

$210x = 100x - 232$

$210x - 100x = - 232$

$110x = - 232 \implies \bf x = - 2.1(09)$