Вправа 841 алгебра Бевз гдз 7 клас

$$
\begin{aligned}
&\text { № } 841\\
&\begin{aligned}
& \text { a) } 4-(x-3)^2=0 \\
& (2-x+3)(2+x-3)=0 \\
& (6-x)(x-1)=0 \\
& x_1=6 ; x_2=1
\end{aligned}\\
&\begin{aligned}
& \text { 6) }(5 x+4)^2=196 \\
& (5 x+4) 2-142=0 \\
& (5 x+4-14)(5 x+4+14)=0 \\
& (5 x-10)(5 x+18)=0 \\
& \text { 1) } 5 x-10=0 \\
& 5 x=10 \\
& x_1=4
\end{aligned}
\end{aligned}
$$
$$
\text { 2) } \begin{gathered}
5 x+18=0 \\
5 x=18 \\
x_2=3 \frac{3}{5}
\end{gathered}
$$
$$
\begin{aligned}
& \text { B) }(3 x-2)^2-(x+6)^2=0 \\
& \text { ( } 3 x-2-x-6)(4 x+4)=0 \\
& \text { 1) } 2 x-8=0 \\
& 2 x=8 \\
& x_1=4
\end{aligned}
$$
$$
\begin{gathered}
2) 4 x+4=0 \\
4 x=-4 \\
x_2=-1
\end{gathered}
$$
$$
\begin{aligned}
& \text { г) }(2 x-1)^2=(4-5 x)^2 \\
& (2 x-1)^2-(4-5 x)^2=0 \\
& (2 x-1-4+5 x)(2 x-1+4-5 x)=0 \\
& (7 x-5)(3-3 x)=0 \\
& \text { 1) } 7 x-5=0 \\
& 7 x=5 \\
& \quad x_1=\frac{5}{7}
\end{aligned}
$$
$$
\text { 2) } \begin{gathered}
3-3 x=0 \\
-3 x=-3 \\
x_2=1
\end{gathered}
$$

ґ) (2х + 1)(4х² – 2х + 1) = 4х(2х² – 5)
8х³ + 125 = 8х³ – 20х
20х = –125
х = –6,25;

д) х(8х² – 5) = (4х² – 10х + 25)(2х + 5)
8х³ – 5х = 8х³ + 125
–5х = 125
х = 125 : (–5)
х = –25.

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