Toán Lớp 8: a, x ²-x=0 b, 5x ²+30x=0 c, 2x ²=8x d, 9x ²-4=0 e, 16=25x ² g,3x(x+1)+(x+1)(x-3)=0 h, (x-2)(3x-5)-(x-2)(x+1)=0 Trả lời chi tiết đầy đủ

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Toán Lớp 8:  a, x ²-x=0 b, 5x ²+30x=0 c, 2x ²=8x d, 9x ²-4=0 e, 16=25x ² g,3x(x+1)+(x+1)(x-3)=0 h, (x-2)(3x-5)-(x-2)(x+1)=0 Trả lời chi tiết đầy đủ hứa vote5*

ngocbichchau · Answer

Giải đáp+Lời giải và giải thích chi tiết: a, x ^2-x=0 <=>x(x-1)=0 <=>$ left[ begin{matrix} x=0 x-1=0 end{matrix} right.$ <=>$ left[ begin{matrix} x=0 x=1 end{matrix} right.$ Vậy x_1=0;x_2=1 b, 5x ^2+30x=0 <=>5x(x+6)=0 <=>$ left[ begin{matrix} 5x=0 x+6=0 end{matrix} right.$ <=>$ left[ begin{matrix} x=0 x=-6 end{matrix} right.$ Vậy x_1=0;x_2=-6 c, 2x ^2=8x <=>2x^2-8x=0 <=>2x(x-4)=0 <=>$ left[ begin{matrix} 2x=0 x-4=0 end{matrix} right.$ <=>$ left[ begin{matrix} x=0 x=4 end{matrix} right.$ Vậy x_1=0;x_2=4 d, 9x ^2-4=0 <=>(3x-2)(3x+2)=0 <=>$ left[ begin{matrix} 3x-2=0 3x+2=0 end{matrix} right.$ <=>$ left[ begin{matrix} 3x=2 3x=-2 end{matrix} right.$ <=>$ left[ begin{matrix} x=2/3 x=-2/3 end{matrix} right.$ Vậy x_1=2/3;x_2=-2/3 e, 16=25x^2 <=>16-25x^2=0 <=>(4-5x)(4+5x)=0 <=>$ left[ begin{matrix} 4-5x=0 4+5x=0 end{matrix} right.$ <=>$ left[ begin{matrix} 5x=4 5x=-4 end{matrix} right.$ <=>$ left[ begin{matrix} x=4/5 x=-4/5 end{matrix} right.$ Vậy x_1=4/5;x_2=-4/5 g,3x(x+1)+(x+1)(x-3)=0 <=>(x+2)[3x+(x-3)]=0 <=>(x+2)[3x+x-3]=0 <=>(x+2)(4x-3)=0 <=>$ left[ begin{matrix} x+2=0 4x-3=0 end{matrix} right.$ <=>$ left[ begin{matrix} x=-2 4x=3 end{matrix} right.$ <=>$ left[ begin{matrix} x=-2 x=3/4 end{matrix} right.$ h, (x-2)(3x-5)-(x-2)(x+1)=0 <=>(x-2)[(3x-5)-(x+1)=0 <=>(x-2)(3x-5-x-1)=0 <=>(x-2)(2x-6)=0 <=>2(x-2)(x-3)=0 <=>$ left[ begin{matrix} x-2=0 x-3=0 end{matrix} right.$ <=>$ left[ begin{matrix} x=2 x=3 end{matrix} right.$ Vậy x_1=2;x_2=3

hatuanlan · Answer

$ text{a) x&sup2; - x = 0}$   $ text{&hArr; x(x - 1) = 0}$   $ text{&hArr; $ left[ begin{matrix} x = 0   x - 1 = 0 end{matrix} right.$}$   $ text{&hArr; $ left[ begin{matrix} x = 0   x = 1 end{matrix} right.$}$   $ text{Vậy x &isin; {0; 1}}$   $ text{b) 5x&sup2; + 30x = 0}$   $ text{&hArr; 5x(x + 6) = 0}$   $ text{&hArr; $ left[ begin{matrix} 5x = 0   x + 6 = 0 end{matrix} right.$}$   $ text{&hArr; $ left[ begin{matrix} x = 0   x = -6 end{matrix} right.$}$   $ text{Vậy x &isin; {0; -6}}$   $ text{c) 2x&sup2; = 8x}$   $ text{&hArr; 2x&sup2; - 8x = 0}$   $ text{&hArr; 2x(x - 4) = 0}$   $ text{&hArr; $ left[ begin{matrix} 2x = 0   x - 4 = 0 end{matrix} right.$}$   $ text{&hArr; $ left[ begin{matrix} x = 0   x = 4 end{matrix} right.$}$   $ text{Vậy x &isin; {0; 4}}$   $ text{d) 9x&sup2; - 4 = 0}$   $ text{&hArr; (3x - 2)(3x + 2) = 0}$   $ text{&hArr; $ left[ begin{matrix} 3x - 2 = 0  3x + 2 = 0 end{matrix} right.$}$   $ text{&hArr; $ left[ begin{matrix} x =  dfrac{2}{3}   x = - dfrac{2}{3} end{matrix} right.$}$   $ text{Vậy x &isin; {&plusmn;$ dfrac{2}{3}$}}$   $ text{e) 16 = 25x&sup2;}$   $ text{&hArr; 16 - 25x&sup2; = 0}$   $ text{&hArr; (4 - 5x)(4 + 5x) = 0}$   $ text{&hArr; $ left[ begin{matrix} 4 - 5x = 0  4 + 5x = 0 end{matrix} right.$}$   $ text{&hArr; $ left[ begin{matrix} x =  dfrac{4}{5}   x = - dfrac{4}{5} end{matrix} right.$}$   $ text{Vậy x &isin; {&plusmn;$ dfrac{4}{5}$}}$   $ text{g) 3x(x + 1) + (x + 1)(x - 3) = 0}$   $ text{&hArr; (x + 1)(3x + x - 3) = 0}$   $ text{&hArr; (x + 1)(4x - 3) = 0}$   $ text{&hArr; $ left[ begin{matrix} x + 1 = 0  4x - 3 = 0 end{matrix} right.$}$   $ text{&hArr; $ left[ begin{matrix} x = -1   x =  dfrac{3}{4} end{matrix} right.$}$   $ text{Vậy x &isin; {-1; $ dfrac{3}{4}$}}$   $ text{h) (x - 2)(3x - 5) - (x - 2)(x + 1) = 0}$   $ text{&hArr; (x - 2)(3x - 5 - x - 1) = 0}$   $ text{&hArr; (x - 2)(2x - 6) = 0}$   $ text{&hArr; $ left[ begin{matrix} x  - 2 = 0  2x - 6 = 0 end{matrix} right.$}$   $ text{&hArr; $ left[ begin{matrix} x = 2   x = 3 end{matrix} right.$}$   $ text{Vậy x &isin; {2; 3}}$   $ textit{Ha1zzz}$

Toán Lớp 8: a, x ²-x=0 b, 5x ²+30x=0 c, 2x ²=8x d, 9x ²-4=0 e, 16=25x ² g,3x(x+1)+(x+1)(x-3)=0 h, (x-2)(3x-5)-(x-2)(x+1)=0 Trả lời chi tiết đầy đủ

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