Question

70 баллов дам!!
Помогите решить пожалуйста, кто знает

Answer 1

Ответ:

$1)d = - 8.5 \ a1 = - 6.8 \ a5 = a1 + 4d = - 6.8 + 4 times ( - 8.5) = - 40.8 \ 2) ....- 6.x. - 2.0...... \ \ x = frac{ - 6 + ( - 2)}{2} = - 4$

$3)a10 = - 10 : : : : a10 = a1 + 9d\ a16 = - 19 : : : : a16 = a1 + 15d\ \ a1 + 9d = - 10 \ a1 + 15d = - 19 \ a1 + 15d - a1 - 9d = - 19 - ( - 10)\ 6d = - 9 \ d = - 1.5$

$4)d = 1.1 \ a1 = - 7 \ s8 = frac{2a1 + 7d}{2} times 8 = \ = frac{2 times ( - 7) + 7 times 1.1}{2} times 8 = \( - 14 + 7.7) times 4 = - 6.3 times 4 = - 25.2$

$5)20.13.6.... \ a1 = 20 \ a2 = 13\ d = 13 - 20 = - 7 \ a7 = a1 + 6d = \ = 20 + 6 times ( - 7) = 20 - 42 = - 22$

$6)100.20.4..... \ b1 = 100 \ b2 = 20 \ q = frac{b2}{b1} = frac{20}{100} = frac{1}{5} \ b5 = b1 times {q}^{4} = 100 times {( frac{1}{5} )}^{4} = \ = 100 times frac{1}{25 times 25} = frac{4}{25} = 0.16$

$7)...3.x.75. - 375.... \ \ {x}^{2} = 3 times 75 \ x = sqrt{3 times 75} = \ = sqrt{3 times 3 times 5 times 5} = 3 times 5 = 15$

$9)b1 = - 3 \ b(n + 1) = - 4bn \ b2 = - 4 times ( - 3) = 12 \ q = frac{12}{ - 3} = - 4 \ s5 = frac{b1( {q}^{n} - 1)}{ q - 1} = \ = frac{ - 3( {( - 4)}^{5} - 1 ) }{ - 4 - 1} = \ = frac{3 times 1024}{5} = 614.4$

$8)b1 = - 6 \ b(n + 1) = 2bn \b2 = 2b1 = 2 times ( - 6 ) = - 12 \ q = frac{b2}{b1} = frac{ - 12}{ - 6} = 2 \ b6 = b1 times {q}^{5} = \ = - 6 times {2}^{5} = - 6 times 32 = - 192$

$10) - 1250. - 250. - 50..... \ q = frac{ - 250}{ - 1250} = frac{1}{5} \ b4 = - 50 times frac{1}{5} = - 10 \ b5 = - 10 = frac{1}{5} = - 2 \ s5 = - 1250 - 250 - 50 - 10 - 2 = \ = 1562$