B3=3/4 q=-1/2 s4?
b3=b1*q² b1*1/4=3/4 b1=3
формула суммы n членов sn=b1*(1-qⁿ)/(1-q)
s4=3*(1-(-1/2)⁴)/(3/2)=3*(1-1/16)/(3/2)
s4=3*15*2/16*3=90/48=1.875
см.рис
y=2(x+3)/7
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Он равен 1..................
1) <span>12b² - 12c²=12(b-c)(b+c)
2) </span><span>2a²c - 2b²c=2c(a-b)(a+b)
3)</span><span>5a² - 20=5(a-2)(a+2)
4)</span><span>3mn² - 48m=3m(n-4)(n+4)
</span><span>5) 7y³ - 7y=7y(y-1)(y+1);
6) a³ - a⁵=a</span>³(1-a)(1+a)<span>;</span>