1/25a^2+1/10ab+1/16b^2=(1/5a+1/4b)^2; 0,09a^2-4b^2=(0,3a-2b)(0,3a+2b); 16a^2b^2-48abc+36c^2=4(4a^2b^2-12abc+9c^2)=4(2ab-3c)^2; 25x^2+30xy+9y^2=(5x+3y)^2; a^2-6a+9/a-3=(a-3)^2/(a-3)=a-3.
30 г ------100%
х -------- 4%
х=(30*4)/100=120/100=1,2 (г)
<span>(х^2-4)*(х+7)>=0
(x+2)(x-2)(x+7)>=0
-------(-7)-------(-2)--------(2)------
-7<=x<= -2
x>=2</span>
Сosacosb-sinasinb=cos(a+b)
cos24cos31-sin2xsin31=cos(24+31)=cos55