Giúp mik với Câu 1. Phân tích các đa thức sau thành nhân tử: a) $x^{2}$ - 25 b) $x^{2}$ + 2xy - 3x - 6y Câu 2. a) Tìm x biết: 2$x^{2}$ - 10x = 0 b) Tính nhanh: $24^{2}$ + 48. 36 + $36^{2}$ Câu 3. Làm tính chia: a) ($x^{2}$$y^{4}$

Nguyen22

2 năm trước

Giúp mik với Câu 1. Phân tích các đa thức sau thành nhân tử: a) $x^{2}$ - 25 b) $x^{2}$ + 2xy - 3x - 6y Câu 2. a) Tìm x biết: 2$x^{2}$ - 10x = 0 b) Tính nhanh: $24^{2}$ + 48. 36 + $36^{2}$ Câu 3. Làm tính chia: a) ($x^{2}$$y^{4}$ – 10$x^{3}$$y^{2}$ + 15x$y^{3}$ ): (-5x$y^{2}$ ) b) (2$x^{4}$ - 10$x^{3}$ – $x^{2}$ +15x - 3): (2$x^{2}$ - 3) Câu 4. Cho hình chữ nhật ABCD. Gọi H là chân đường vuông góc kẻ từ A đến BD. Gọi M và N theo thứ tự là trung điểm của AH và DH. a) Chứng minh MN//AD b) Gọi I là trung điểm của BC. Chứng minh tứ giác BMNI là hình bình hành. c) Tính góc ANI. Câu 5. (1 điểm) Cho a, b, c là các số dương thỏa mãn $a^{3}$ + $b^{3}$ + $c^{3}$ = 3abc. Tính giá trị biểu thức: P = ($\frac{a}{b}$ -1) + ( $\frac{b}{c}$ -1) + ( $\frac{c}{a}$ - 1)

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ngochuyenn928

Bài 1:

$a) x^2−25$

$⇒ x^2−5^2$

$⇒(x−5)(x+5)$

$b) x^2+2xy−3x−6y$

$⇒x(x+2y)−3(x+2y)$

$⇒(x+2y)(x−3)$

Bài 2:

$a) 2x^2−10x=0$

$⇔2x(x−5)=0$

$⇔x(x−5)=0$

$⇔\left \{ {{x=0} \atop {x-5=0}} \right.$

$⇔\left \{ {{x=0} \atop {x=5}} \right.$

$b) 24^2+48.36+36^2$

$⇔24^2+2.24.36+36^2$

$⇔(24+36)^2$

$⇔80^2$

$⇔6400$

Bài 4:

$a)$ Xét $ΔADH$ có $M$ là trung điểm của $AH$

$N$ là trung điểm của $DH$

$⇒ MN$ là đường trung bình của $ΔADH$

$⇒ MN//AD$

$b)$ $MN//AD//BC ⇒ MN//BI$

$MN//AD ⇒ MN=\frac{1}{2}AD=$ $\frac{1}{2}BC=BI$

⇒ Tứ giác $BMNI$ là hình bình hành

$c)$ Ta có:

$AH ⊥DB$

$⇒ AM⊥NB$
$MN//AD$

Mà $AD⊥AB ⇒ MN⊥AB$
⇒ $M$ là trực tâm

$⇒ BM⊥AN$
Mà $BM//NI$
$⇒ NI⊥AN$
$⇒ ΔANI ⊥ N$

Chúc bạn học tốt!!!

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huongweibo

Đáp án:

Giải thích các bước giải:

câu 1

a, $x^2 - 25 $

$= x^2 - 5^2 $

$= (x - 5 ) ( x + 5 ) $

b, $x^2 + 2xy - 3x - 6y $

$= x(x + 2y) - 3( x + 2y ) $

$= ( x + 2y ) ( x - 3 ) $

câu 2

a, $2x^2 - 10x = 0 $

$⇔ 2x( x - 5 ) = 0$

$⇔ x( x -5 ) = 0 $

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

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

b, $24^2 + 48 . 36 + 36^2 $

$= 24^2 + 2.24.36 + 36^2 $

$= ( 24 + 36 ) ^2 $

$= 80^2 $

$= 6400 $

câu 3

a) $ (x^2y^4 - 10x^3y^2 + 15xy^3 ) : ( -5xy^2 ) $

$= [ xy^2( xy^2 - 10x^2 + 15y ) : ( -5xy^2 ) $

$= ( xy^2 - 10^2 + 15y) : ( -5 ) $

$= ... $

b, $(2x^4 - 10x^3 - x^2 + 15x - 3 ) : ( 2x^2-3 ) $

$= ... $

mik chỉ lm đc thế này thôi !!! mog bn thông cảm !!!

Chúc bn hok tốt !!!!

Vote (0) Phản hồi (0) 2 năm trước

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