Question

Срочно одам 70балов ​

Answer 1

Ответ:

Применяем формулы сокращённого умножения:

$\bf (a\pm b)^2=a^2\pm 2ab+b^2\ ,\ \ (a-b)(a+b)=a^2-b^2$    

$1)\ \ y(y-2)-(y+3)^2=1\\\\y^2-2y-(y^2+6y+9)=1\\\\-8y-9=1\\\\8y=-10\\\\\bf y=-1,25$  

$2)\ \ (2y-3)^2-(2y+5)^2=16\\\\4y^2-12y+9-(4y^2+20y+25)=16\\\\-32y-16=16\\\\-32y=32\\\\\boldsymbol{y=-1}\\\\\\ili\ \ \ \ \Big((2y-3)-(2y+5)\Big)\Big((2y-3)+(2y+5)\Big)=16\\\\{}\ \ \ \ \ \ -8\cdot (4y+2)=16\\\\{}\ \ \ \ \ \ \, -32y-16=16\\\\{}\ \ \ \ \ \ \, -32y=32\\\\{}\qquad \ \ \ \ \bf y=-1$

$3)\ \ (6y-5)^2+(5-3y)(12y-2)=4(y-18)\\\\36y^2-60y+25+60y-10-36y^2+6y=4y-72\\\\6y+15=4y-72\\\\2y=-87\\\\\bf y=-43,5$  

$4)\ \ (5y-4)^2-(3y-2)(3y+2)=2y(8y-5)\\\\25y^2-40y+16-(9y^2-4)=16y^2-10y\\\\16y^2-40y+20=16y^2-10y\\\\-30y=-20\\\\\bf y=\dfrac{2}{3}$