(2x - 5)^2 = 4x^2 - 9
4x^2 - 20x + 25 = 4x^2 - 9
4x^2 - 20x + 25 - 4x^2 + 9 = 0
- 20x + 34 = 0
- 20x = - 34
x = 34/20
x = 1,7
Ответ:
Объяснение:
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А) sin(45+30)=sin45cos30+sin30cos45=sqrt(2)/2*sqrt(3)/2+1/2*sqrt(2)/2=(sqrt(3)+1)/(2*sqrt(2))
б) cos(135/2)=sqrt((1+cos135)/2)=sqrt{(1-sqrt(2)/2)/2}=sqrt((2-sqrt2)/4)=(sqrt(2-sqrt2))/2