Tìm x biết : a. (5x-4)^2 – 49x^2 = 0 b. x^2 +3x-10 =0

Question

Question

Tìm x biết :
a. (5x-4)^2 – 49x^2 = 0
b. x^2 +3x-10 =0

in progress 0

Môn Toán Edana Edana 6 years 2020-10-15T12:12:10+00:00 2020-10-15T12:12:10+00:00 2 Answers 381 views 0

Answers ( )

Name*

E-Mail*

Website

Featured image

Browse

Captcha* Giải phương trình 1 ẩn: x + 2 - 2(x + 1) = -x . Hỏi x = ? ( )

Answer*

Gerda · Answer 1 · 2020-10-15T12:13:35+00:00

`a,` `(5x-4)^2-49x^2=0`

`⇔(5x-4)^2-(7x)^2=0`

`⇔(5x-4-7x)(5x-4+7x)=0`

`⇔(-2x-4)(12x-4)=0`

$⇔\left[ \begin{array}{l}-2x-4=0\\12x-4=0\end{array} \right.⇔\left[ \begin{array}{l}x=-2\\x=\dfrac13\end{array} \right.$

`b,` `x^2+3x-10=0`

`⇔x^2-2x+5x-10=0`

`⇔x(x-2)+5(x-2)=0`

`⇔(x+5)(x-2)=0`

$⇔\left[ \begin{array}{l}x+5=0\\x-2=0\end{array} \right.⇔\left[ \begin{array}{l}x=-5\\x=2\end{array} \right.$

Jezebel · Answer 2 · 2020-10-15T12:14:08+00:00

Đáp án:

a)$\left[ \begin{array}{l}x=-2\\x=\dfrac{1}{3}\end{array} \right.$

b)$\left[ \begin{array}{l}x=2\\x=-5\end{array} \right.$

Giải thích các bước giải:

$a)(5x-4)^2-49x^2=0$

$⇔(5x-4-7x).(5x-4+7x)=0$

$⇔(-2x-4).(12x-4)=0$

⇔$\left[ \begin{array}{l}-2x-4=0\\12x-4=0\end{array} \right.$

⇔$\left[ \begin{array}{l}x=-2\\x=\dfrac{1}{3}\end{array} \right.$

$b)x^2+3x-10=0$

$⇔x^2-2x+5x-10=0$

$⇔x.(x-2)+5.(x-2)=0$

$⇔(x-2).(x+5)=0$

$\left[ \begin{array}{l}x-2=0\\x+5=0\end{array} \right.$

$\left[ \begin{array}{l}x=2\\x=-5\end{array} \right.$