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![](https://rs.olm.vn/images/avt/0.png?1311)
Bị tự tin quá khả năng nhẩm mồm, sai em xin lỗi ...
a, Ta có \(P\left(x\right)=8x^3+2x^2-3x-3x^3+10-x-2x^2-3\)
\(=5x^3-4x-7\)
\(Q\left(x\right)=9x^3-4x^2+2x-3+2x+3x^2+4x^3-2\)
\(=13x^3-x^2+4x-5\)
b, Ta có : \(P\left(-\frac{1}{2}\right)=5.\left(-\frac{1}{2}\right)^3-4.\left(-\frac{1}{2}\right)-7=-\frac{45}{8}\)
c , \(M\left(x\right)=P\left(x\right)+Q\left(x\right)\)
\(5x^3-4x-7+13x^3-x^2+4x-5=18x^3-x^2-12\)
\(N\left(x\right)=P\left(x\right)-Q\left(x\right)\)
\(5x^3-4x-7-13x^3+x^2-4x+5=-8x^3-8x-2+x^2\)
d, Đặt \(5x^3-4x-7=0\)( vô nghiệm )
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a.xz+yz-5\left(x+y\right)=\left(x+y\right)z-5\left(x+y\right)\)
\(=\left(x+y\right)\left(z-5\right)\)
Học tốt
a, xz + yz - 5(x + y)
<=> z(x + y) - 5(x + y)
<=> (z - 5).(x + y)
b, x2 - 3xy + 2y2
<=> x2 - xy - 2xy + 2y2
<=> x(x - y) - 2y(x - y)
<=> (x - 2y).(x - y)
![](https://rs.olm.vn/images/avt/0.png?1311)
Câu 1:
a: \(=a^2+2ab+b^2-a^2-2ab-b^2=0\)
b: \(=x^3+27-54-x^3=-27\)
Câu 4:
\(\Leftrightarrow3x^3+x^2+9x^2+3x-3x-1-4⋮3x+1\)
\(\Leftrightarrow3x+1\in\left\{1;-1;2;-2;4;-4\right\}\)
hay \(x\in\left\{0;1\right\}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 1:
a) 2x(x2 - 3x + 4)
= 2x3 - 6x2 + 8x
b) (x + 2)(x - 1)
= x2 - x + 2x - 2
= x2 + x - 2
c) (4x4 - 2x3 + 6x2) : 2x
= 2x3 - x2 + 3x
Bài 2:
a) 2x2 - 6x
= 2x(x - 3)
b) 2x2 - 18
= 2(x2 - 9)
= 2(x - 3)(x + 3)
c) x3 + 3x2 + x + 3
= x2(x + 3) + (x + 3)
= (x + 3)(x2 + 1)
Bài 1 :
a) \(2x\left(x^2-3x+4\right)\)
= \(2x^3-6x^2+8x\)
b) \(\left(x+2\right)\left(x-1\right)\)
\(=x^2-x+2x-2\)
\(=x^2-x-2\)
Bài 2 :
a) \(2x^2-6x\)
\(=2x\left(x-3\right)\)
b) \(2x^2-18\)
\(=2\left(x^2-9\right)\)
\(=2\left(x-3\right)\left(x+3\right)\)
c) \(x^3+3x^2+x+3\)
\(=\left(x^3+3x^2\right)\left(x+3\right)\)
\(=x^2\left(x+3\right)\left(x+3\right)\)
\(=\left(x^2+1\right)\left(x+3\right)\)
Bài 3 :
a) \(\dfrac{5x}{x-1}+\dfrac{-5}{x-1}=\dfrac{5x+\left(-5\right)}{x-1}=\dfrac{5\left(x-1\right)}{x-1}=5\)
b) \(\dfrac{1}{x-3}+\dfrac{2}{x+3}+\dfrac{9-x}{x^2-9}\)
\(=\dfrac{1}{x-3}+\dfrac{2}{x+3}+\dfrac{9-x}{\left(x-3\right)\left(x+3\right)}\)
\(=\dfrac{\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}+\dfrac{2x-6}{\left(x-3\right)\left(x+3\right)}+\dfrac{9-x}{\left(x-3\right)\left(x+3\right)}\)
\(=\dfrac{x+3+2x-6+9-x}{\left(x-3\right)\left(x+3\right)}\)
\(=\dfrac{2x+6}{\left(x-3\right)\left(x+3\right)}=\dfrac{2\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}=\dfrac{2}{x-3}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(5x-4\right)\left(2x+3\right)=10x^2+15x-8x-12=10x^2+7x-12\)
\(b,\frac{x-4}{x-2}+\frac{5x-8}{x-2}=\frac{x-4+5x-8}{x-2}=\frac{6\left(x-2\right)}{x-2}=6\)
\(c,\frac{x-9}{x^2-9}-\frac{3}{x^2+3x}=\frac{x-9}{\left(x+3\right)\left(x-3\right)}-\frac{3}{x\left(x+3\right)}\)
\(=\frac{x^2-9x}{x\left(x+3\right)\left(x-3\right)}-\frac{3x-9}{x\left(x+3\right)\left(x-3\right)}=\frac{x^2-9x-3x+9}{x\left(x+3\right)\left(x-3\right)}=\frac{x^2-6x+9}{x\left(x+3\right)\left(x-3\right)}\)
\(=\frac{x-3}{x\left(x+3\right)}\)
CÂU 1 :
a, ( 5x-4 ) ( 2x + 3 )
= 10x + 15x -8x -12
= 17x - 12
b, \(\frac{x-4}{x-2}\)+ \(\frac{5x-8}{x-2}\)
= \(\frac{x-4+5x-8}{x-2}\)
= \(\frac{6x-12}{x-2}\)
= \(\frac{6\left(x-2\right)}{x-2}\)
= 6
c, \(\frac{x-9}{x^2-9}\)- \(\frac{3}{x^2+3x}\)
= \(\frac{x-9}{\left(x-3\right)\left(x+3\right)}\)- \(\frac{3}{x\left(x+3\right)}\)
= \(\frac{\left(x-9\right).x}{x\left(x-3\right).\left(x+3\right)}\)- \(\frac{3.\left(x-3\right)}{x\left(x-3\right)\left(x+3\right)}\)
= \(\frac{x^2-9x}{x\left(x-3\right)\left(x+3\right)}\)- \(\frac{3x-9}{x\left(x-3\right)\left(x+3\right)}\)
= \(\frac{x^2-9x-3x+9}{x\left(x-3\right)\left(x+3\right)}\)
= \(\frac{x^2-12x+9}{x\left(x-3\right)\left(x+3\right)}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Câu 1:
\(Tacó\)
\(\frac{2}{2x-1}+\frac{4x^2+1}{4x^2-1}-\frac{1}{2x+1}=\frac{2}{2x-1}+\frac{4x^2+1}{\left(2x+1\right)\left(2x-1\right)}-\frac{1}{2x+1}\)
\(=\frac{4x+2}{\left(2x+1\right)\left(2x-1\right)}+\frac{4x^2+1}{\left(2x+1\right)\left(2x-1\right)}-\frac{2x-1}{\left(2x+1\right)\left(2x-1\right)}\)
\(=\frac{4x+2+4x^2+1-2x+1}{\left(2x+1\right)\left(2x-1\right)}=\frac{2x\left(2x+1\right)+4}{\left(2x+1\right)\left(2x-1\right)}=\frac{2x+4}{2x-1}\)
\(b,x=\frac{1}{2}\Rightarrow2x-1=0\left(loại\right)\)
..... 2 câu sau easy
1:
a: 5x(x^2-2x+1)
=5x*x^2-5x*2x+5x*1
=5x^3-10x^2+5x
b: \(M\left(x\right)+N\left(x\right)\)
=8x^2-2x+7+x^2+2x-9
=9x^2-2
c: C(x)=0
=>-3x+9=0
=>-3x=-9
=>x=3
2:
a: Xét ΔAMN và ΔAEP có
AM=AE
góc MAN=góc EAP
AN=AP
=>ΔAMN=ΔAEP
b: ΔAMN=ΔAEP
=>góc AMN=góc AEP
=>MN//EP
mà MN vuông góc MP
nên EP vuông góc MP
c: ΔMPN vuông tại M có MA là trung tuyến
nên MA=1/2NP