Составим уравнение: х + 4х/10 + х/3 = 520
общий знамекнатель: 30.
30х/30 + 12х/30 + 10x/30 = 520
52x/30 = 520
х/30 = 10
x = 10*30
x=300
1) 300 страниц - в 1 книге
2) 300* 0,4 = 120 (стр.) - во второй книге
3) 300/3 = 100 (стр.) 0 в третьей книге
Ответ: 300, 120, 100
X^2=-2x
x^2+2x=0
x*(x+2)=0
x=0
x+2=0
x=0; x=-2.
Решение 100*(100+1):2=5050
\![\frac{ctg(270-\alpha)}{1-tg^2(\alpha-180)}*\frac{ctg^2(360-\alpha)-1}{ctg(180+\alpha)}=\frac{tg\alpha}{1-tg^2\alpha}*\frac{ctg^2\alpha-1}{ctg\alpha}=](https://tex.z-dn.net/?f=%5Cfrac%7Bctg%28270-%5Calpha%29%7D%7B1-tg%5E2%28%5Calpha-180%29%7D%2A%5Cfrac%7Bctg%5E2%28360-%5Calpha%29-1%7D%7Bctg%28180%2B%5Calpha%29%7D%3D%5Cfrac%7Btg%5Calpha%7D%7B1-tg%5E2%5Calpha%7D%2A%5Cfrac%7Bctg%5E2%5Calpha-1%7D%7Bctg%5Calpha%7D%3D+)
![=\frac{tg\alpha}{tg\alpha*ctg\alpha-tg^2\alpha}*\frac{ctg^2\alpha-tg\alpha*ctg\alpha}{ctg\alpha}=\frac{tg\alpha}{tg\alpha(ctg\alpha-tg\alpha)}*\frac{ctg\alpha(ctg\alpha-tg\alpha)}{ctg\alpha}=1](https://tex.z-dn.net/?f=%3D%5Cfrac%7Btg%5Calpha%7D%7Btg%5Calpha%2Actg%5Calpha-tg%5E2%5Calpha%7D%2A%5Cfrac%7Bctg%5E2%5Calpha-tg%5Calpha%2Actg%5Calpha%7D%7Bctg%5Calpha%7D%3D%5Cfrac%7Btg%5Calpha%7D%7Btg%5Calpha%28ctg%5Calpha-tg%5Calpha%29%7D%2A%5Cfrac%7Bctg%5Calpha%28ctg%5Calpha-tg%5Calpha%29%7D%7Bctg%5Calpha%7D%3D1)
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<span>343:98=x:60
98х=343*60
98х=20580
х=20580:98
х=210
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343:98=210:60
3,5=3,5
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