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a. 5x.(12x + 7) - 3x(20x - 5) = - 100
↔ 60x2 + 35x - 60x2 + 15x = - 100
↔ 50x = - 100
→ x = - 2
b. 0,6x(x - 0,5) - 0,3x(2x + 1,3) = 0,138
↔ 0,6x2 - 0,3x - 0,6x2 - 0,39x = 0,138
↔ - 0,6x = 0,138
↔ x = 0,138 : (- 0,6)
↔ x = - 0,2
a) \(5x\left(12x+7\right)-3x\left(20x-5\right)=-100\\ \Leftrightarrow60x^2+35x-60x^2+15x=-100\Leftrightarrow50x=-100\Leftrightarrow x=-2\)
b) câu này nó cứ lộn lộn kiểu gì ý:vvvvô tình muốn giúp nhưng đíu bt đúng hay sai:vv
\(6x\left(x-0,5\right)-0.3x\left(2x+1.3\right)=0,138\\ \Leftrightarrow6x^2-3x-0,6x^2-0,39x=0,138\Leftrightarrow5,4x^2-3,39x=0,138\)
tới này thôi:vvv
1)
a) \(x\left(2x+1\right)-x^2\left(x+2\right)+\left(x^3-x+3\right)\)
\(=2x^2+x-x^3-2x^2+x^3-x+3=3\)
=>đpcm
b) \(4\left(x-6\right)-x^2\left(2+3x\right)+x\left(5x-4\right)+3x^2\left(x-1\right)\)
\(=4x-24-2x^2-3x^3+5x^2-4x+3x^3-3x^2=-24\)
=>đpcm
2,
a) \(5x\left(12x+7\right)-3x\left(20x-5\right)=-100\)
\(\Leftrightarrow60x^2+35x-60x^2+15x=-100\)
\(\Leftrightarrow50x=-100\)
\(\Leftrightarrow x=-2\)
b) \(0,6x\left(x-0,5\right)-0,3x\left(2x+1,3\right)=0,138\)
\(\Leftrightarrow0,6x^2-0,3x-0,6x^2-0,39x=0,138\)
\(\Leftrightarrow-0,69x=0,138\)
\(\Leftrightarrow x=-0,2\)
Câu 1:
a)\(x\left(2x+1\right)-x^2\left(x+2\right)+\left(x^2-x+3\right)\)
\(=2x^2+x-x^3-2x^2+x^2-x+3\)
\(=x^3+3\)(ko thể CM)
b)\(4\left(x-6\right)-x^2\left(2+3x\right)+x\left(5x-4\right)+3x^2\left(x-1\right)\)
\(=4x-24-2x^2-3x^3+5x^2-4x+3x^3-3x^2\)
\(=-24\)(đpcm)
Giải tiêu biểu câu a nhé.
a/ \(5x\left(2x-7\right)+2x\left(8-5x\right)=5\)
\(\Leftrightarrow19x+5=0\)
\(\Leftrightarrow x=-\frac{5}{19}\)
a) 4x(3x-7)-6(2x2-5x+1)=12
=>4x.3x-4x.7-6.2x2-6.(-5x)-6.1=12
=>12x2-28x-12x2+30x-6=12
=>2x-6 =12
=>2x =12+6
=>2x =18
=>x =18:2
=>x =6
b)(5x+3)(4x-1)+(10x-7)(-2x+3)=27
=>5x.4x-5x.1+3.4x+3.(-1)+10x.(-2x)+10x.3-7.-(2x)-7.3=27
=>20x2-5x+12x-3-20x2+30x+14x-21=27
=>39x-36 =27
=>39x =27+36
=>39x =63
=>x =63:39
=>x =21/13
c) (8x-5)(3x+2)-(12x+7)(2x-1)=17
=>8x.3x+8x.2-5.3x-5.2-12x.2x-12x.(-1)+7.2x+7.(-1)=17
=>24x2+16x-15x-10-24x2+12x+14x-7=17
=>27x-17 =17
=>27x =17+17
=>27x =34
=>x =34:27
=>x =34/27
d) (5x+9)(6x-1)-(2x-3)(15x+1)=-190
=>30x2-5x+63x-9 - 30x2-2x-45x-3=-190
=>11x-12 =-190
=>11x =-190+12
=>11x =-178
=>x = -178:11
=>x =-178/11
a/ 3x(12x-4)-9x(4x-3)
=36x2-12x-36x2+27x
=(36x2-36x2)-12x+27x
=15x
b/ x(5-2x)+2x(x-1)
=5x-2x2+2x2-2x
=(5x-2x)-(-2x2+2x2)
=3x
c/ 5x(12x+7)-3x(20x-5)
=60x2+35x-60x2+15x
=(60x2-60x2)+(35x+15x)\
=50x
d/ 3x(2x-7)+2x(5-3x)
=6x2-21x+10x-6x2
=(6x2-6x2)+(10x-21x)
=-11x
e/ đề sai hay sao ý ra số to lắm @@
a)\(60x^2+35x-60x^2+15x=100\)
35x+15x=100
50x=100 =>x=2
b)\(10x^2-35x+16x-10x^2=5\)
-35x+16x=5
-19x=5 =>x=-5/19
1) Ta có: \(x^2-4x+4=0\)
\(\Leftrightarrow\left(x-2\right)^2=0\)
\(\Leftrightarrow x-2=0\)
hay x=2
Vậy: S={2}
a) 5x(12x + 7) - 3x(20x - 5) = -100
<=> 60x2 + 35x - 60x2 + 15x = -100
<=> 50x = -100
<=> x = -2
b) 0,6x(x - 0,5) - 0,3x(2x + 1,3) = 0,138
<=> 0,6x2 - 0,3x - 0,6x2 - 0,39x = 0,138
<=> -0,69x = 0,138
<=> x = -0,2
c) 4x(3x - 7) - 6(2x2 - 5x + 1) = 12
<=> 12x2 - 28x - 12x2 + 30x - 6 = 12
<=> 2x - 6 = 12
<=> 2x = 18
<=> x = 9