<span>|7-3x|=3x-7
7-3x>=0 3x<=7 x<=7/3
7-3x=3x-7
6x=14
x=7/3
7-3x<0 3x>7 x>7/3
-(7-3x)=3x-7
3x-7=3x-7 все решения
ответ x=[7/3 +oo)
</span>
B2=b1*q=1*1/3=1/3
b3=b2*q=1/3*1/3=1/9
b4=b3*q=1/9*1/3=1/27 и все складываешь 1/3+1+1/9+1/27=(9+27+3+1)/27=40/27
*я привела к общему знаменателю 27
можно также найти по формуле суммы S
<span><span><span>
18−<span>5<span>(<span>+3</span>)</span></span></span>><span>1−<span>7</span></span></span><span><span>18−<span>5<span>(<span>x+3</span>)</span></span></span>><span>1−<span>7x</span></span></span></span><span><span><span><span>18−<span>5</span></span>−15</span>><span>1−<span>7</span></span></span><span><span><span>18−<span>5x</span></span>−15</span>><span>1−<span>7x</span></span></span></span><span><span><span>3−<span>5</span></span>><span>1−<span>7</span></span></span><span><span>3−<span>5x</span></span>><span>1−<span>7x</span></span></span></span><span><span><span><span><span>−5</span></span>+<span>7</span></span>><span>1−3</span></span><span><span><span><span>−5</span>x</span>+<span>7x</span></span>><span>1−3</span></span></span><span><span><span>2</span>><span>−2</span></span><span><span>2x</span>><span>−2</span></span></span>x> - 1 <span><span>>−1
</span></span>