415-9x(x+2)=100
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415 - 9(x - 2) = 100
415 - 9x + 18 = 100
433 - 9x = 100
9x = 433 - 100
9x = 333
x = 333 : 9
x = 37
Bài 1
415- 2*(x -19)-15=20
<=> 415 - 2x + 38 - 15 = 20
<=> 438 -2x = 20
<=> 2x = 418
<=> x = 209
5*x-14+x=100+4*x
<=> 6x- 14 = 100 + 4x
<=> 2x = 114
<=> x = 57
415-2(x-19)-15=20
415-2x+38-15=20
(415+38-15)-2x=20
438-2x=20
2x=438-20
2x=418
x=418:2
x=204
5x-14+x=100+4x
5x+x-4x=100+14
2x=114
x=114:2
x=57
a: \(\Leftrightarrow x^2\left(9x^2-4\right)=0\)
\(\Leftrightarrow x^2\left(3x-2\right)\left(3x+2\right)=0\)
hay \(x\in\left\{0;\dfrac{2}{3};-\dfrac{2}{3}\right\}\)
b: \(\Leftrightarrow2x^4-4x^2+3x^2-6=0\)
\(\Leftrightarrow x^2-2=0\)
hay \(x\in\left\{\sqrt{2};-\sqrt{2}\right\}\)
d: \(\Leftrightarrow x^4-9x^2+6x^2-54=0\)
\(\Leftrightarrow x^2-9=0\)
=>x=3 hoặc x=-3
\(a.415\times7-415\times5+415\times8\)
\(=415\times\left(7-5+8\right)=415\times10=4150\)
\(b.23\times87+12\times23+23\)
\(=23\times\left(87+12+1\right)=23\times100=2300\)
a. 415 x 7 - 415 x 5 + 4 15 x 8
= 415 x ( 7 - 5 + 8 )
= 415 x 10
= 41 50
b. 23 x 87 + 1 2 x 23 + 2 3
= 23x 87 + 12 x 23 + 23 x 1
= 23 x ( 87 + 12 + 1 )
= 23 x 100
= 2300
=
a) 415 x 7 - 415 x 5 + 415 x 8
= 415 x (7 - 5 + 8)
= 415 x 10
= 4150
b) 23 x 87 + 12 x 23 + 23
= 23 x 87 + 12 x 23 + 23 x 1
= 23 x (87 + 12 + 1)
= 23 x 100
= 2300
Học sinh nhẩm và ghi kết quả như sau:
100 – 50 = 50
950 – 50 =900
515 – 415 =100
\(a,=\left(x-5\right)\left(x+5\right)\\ b,=\left(x-3\right)^2\\ c,=\left(3x-2\right)\left(3x+2\right)\\ d,=\left(x+1\right)^2\\ e,=\left(x-10\right)\left(x+10\right)\)
1. 3x - 17 = x+3
3x - x = 3 + 17
2x = 20
x = 20 :2
x = 10
2. |x-3| - 12 = |-5|
|x-3| -12 = 5
|x-3| = 5 + 12
|x-3| = 17
=> x-3 = +17 , -17
x = 17 + 3
x = 20
x = -17 + 3
x = -14
3 . 25 - ( x -5 ) = -415 -( 15 -415)
25 - x +5 = -415 - 15 +415
25 - x +5 = ( -415 + 415) -15
25 - x +5 = 0-5 = -5
25 - x = -5-5
25 - x = -10
x = 25 - -10
x = 35
4. ( x -3 ) . ( 2x +6 ) = 0
=> x-3 = 0 hoặc 2x +6 = 0
x = 0 + 3 = 3
2x = 0-6=-6
x = -6 : 2
x = -3
\(1;3x-17=x+3\)
\(\Leftrightarrow3x-x=3+17\)
\(\Leftrightarrow2x=20\)
\(\Rightarrow x=10\)
\(2;\left|x-3\right|-12=\left|-5\right|\)
\(\Leftrightarrow\left|x-3\right|-12=5\)
\(\Leftrightarrow\left|x-3\right|=5+12\)
\(\Leftrightarrow\left|x-3\right|=17\)
\(\Rightarrow\orbr{\begin{cases}x-3=17\\3-x=17\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=17+3\\-x=17-3\end{cases}\Leftrightarrow\orbr{\begin{cases}x=20\\x=-14\end{cases}}}\)
\(3;25-\left(x-5\right)=-415-\left(15-415\right)\)
\(\Leftrightarrow25-x+5=-415-15+415\)
\(\Leftrightarrow-x=-415-15+415-25-5\)
\(\Leftrightarrow-x=-45\)
\(\Rightarrow x=45\)
\(4;\left(x-3\right)\left(2x+6\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x-3=0\\2x+6=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=3\\x=-3\end{cases}}}\)
415 - 9 x ( \(x\)+ 2 ) = 100
9 x ( \(x\)+ 2 ) = 415 - 100
9 x ( \(x\)+ 2 ) = 315
\(x\) + 2 = 315 : 9
\(x\)+ 2 = 35
\(x\)= 35 - 2
\(x\)= 33
415-9(x+2)=100
9(x+2)=315
x+2=35
x=33
#H