Вправа 840 алгебра Бевз гдз 7 клас
$$\begin{aligned}
&\text { № } 840\\
&\begin{aligned}
& \text { a) }(x+1)^2-9=0 \\
& (x+1-3)(x+1+3)=0 \\
& (x-2)(x+4)=0 \\
& x_1=2 ; x_2=-4 ;
\end{aligned}\\
&\begin{aligned}
& \text { 6) }(3 x-2)^2=121 \\
& (3 x-2)^2-11^2=0 \\
& (3 x-2-11)(3 x-2+11)=0 \\
& (3 x-13)(3 x+9)=0 \\
& 3 x-13=0 \\
& 3 x=13 \\
& x_1=4 \frac{1}{3}
\end{aligned}
\end{aligned}
$$
$$
\begin{aligned}
& 3 x+9=0 \\
& 3 x=-9 \\
& x_2=-3
\end{aligned}
$$
в) (x – 1)2 – (3 – x)2 = 0
(х – 1 – 3 + х)(х – 1 + 3 – х) = 0
(2х – 4) • 2 = 0
2х – 4 = 0
2х = 4
х = 2;
г) (4x – 10)2 = (3x – 4)2
(4х – 10)2 – (3х – 4)2 = 0
(4х – 10 – 3х + 4)(4х – 10 + 3х – 4) = 0
(х – 6)(7х – 14) = 0
1) х – 6 = 0
х1 = 6
2) 7х – 14 = 0
7х = 14
х2 = 2;
ґ) (x2 + x + 1)(x – 1) = x (x2 + 1)
х3 – 1 = х3 + 1
–1 = 1
коренів немає;
$$
\begin{aligned}
& \text { д) }\left(9 x^2+4\right) \cdot 3 x=(3 x+2)\left(9 x^2-6 x+4\right) \\
& 27 x^3+12 x=27 x^3+8 \\
& 12 x=8 \\
& x=8: 12 \\
& x=\frac{2}{3} .
\end{aligned}
$$
вправи поруч
