Question

100 ! найти функцию, обратную данной: а)y=1/6x-12 б)y=4/8-x в)y=-2x*2+7

Answer 1

$1)\quad y= \frac{1}{6x} -12\; ,\; \; \; ODZ:\; x\ne 0\\\\\frac{1}{6x}=y+12\\\\6x=\frac{1}{y+12}\\\\x=\frac{1}{6(y+12)}\\\\Obratnaya \; fynkciya:\; \; y=\frac{1}{6(x+12)}\; ,\; \; \; ODZ:\; x\ne -12\\\\2)\; \; \; y=\frac{4}{8-x}\; ,\; \; \; ODZ:\; \; x\ne 8\\\\8-x=\frac{4}{y}\\\\x=8+\frac{4}{y}\\\\Obratnaya\; fynkciya:\; \; y=8+\frac{4}{x}\; ,\; \; ODZ:\; \; x\ne 0$

$3)\; \; \; y=-2x^2+7\; ,\; \; \; ODZ:\; \; x\in R\\\\2x^2=7-y\\\\x^2=\frac{7-y}{2}$

$Obratnaya\; fynkciya:\; \; \; y^2=\frac{7-x}{2}\; \; \; ili\; \; \; y=\pm \sqrt{\frac{7-x}{2}}\\\\ODZ:\; \; \; 7-x \geq 0\; \; \to \; \; x \leq 7$

Answer 2

Решение
а)y=1/(6x) - 12
6xy + 72x = 1
x*(6y + 72) = 1
x = 1 / (6y + 72)
б) y= 4/(8-x)
(8 - x)*y = 4
8y - xy = 4
xy = 8y - 4
x = (8y - 4)/y
в) y=-2x*2+7
2x² = 7 - y
x² = (7 - y)/2
x = - √[(7 - y)/2]
x = √[(7 - y)/2]