Ph¬ng tr×nh qui vÒ ph¬ng tr×nh bËc hai
Bµi 1 Gi¶i c¸c ph¬ng tr×nh sau:
a) x−6 x +5=0 b) −2x+5 x +7=0 c) − x +8x−9=0
1
20
= +
g) 9x4 +6x2 +1=0 h) 2x4 −5x2 +3=0 i) −x4 +5x2 +6=0
5
100
5
100
=
−
+
2 2
2
=
+ +
x x
x
l)
1
1 2 2
1 2
1
+
+
=
−
− + +
+
x
x x
x x
x
Bµi 2 Gi¶i c¸c ph¬ng tr×nh sau:
a)x5 −x3 −x2 +1=0 b) 6x4 +7x3 −36x2 −7x+6=0 c)2x3 +7x2 +7x +2=0
d) x3 −8x2 −8x+1=0 e) x3 +x2 +4=0 g)x3 −5x2 +8x−4 =0
Bµi 3 Gi¶i c¸c ph¬ng tr×nh sau:
a) x(x+1)(x+2)(x +3)+1=0 b) ( x+2) ( x+3) ( x−7) ( x− =8) 144
c) (x −1)(x−3)(x+5)(x+7) =297 d) (x−1)(x+2)(x+3)(x+6) =108
e) (x−1)(x−3)(x−5)(x −7) =20 f) (4x +1)(12x−1)(3x +2)(x+1) =4
g) (6 5) (2 3 2)( 1) 35
= + +
= + +
x
i) (x +1) (2 2x+1)(2x +3) =18 j) ( x−4) ( x−5) ( x−8) (x−10) =72x2
k) (x+10) ( x+12) ( x+15) ( x+18) =2x2
Bµi 4 Gi¶i c¸c ph¬ng tr×nh sau:
a) (x+3) (4 + x +5)4 =2 b) (x+1) (4 + x−3)4 =82
c) ( 2) (4 6 )4 82
=
− +
=
− +
x
Bµi 5 Gi¶i c¸c ph¬ng tr×nh sau:
a) x4 −10x3 +26x2 −10x+1=0 b) x4 −4x3 −6x2 −4x+1=0
c) x4 +2x3 −x2 −2x+1=0 d) x4 +3x3 −14x2 −6x +4=0
e) x4 −4x3 −9x2 +8x+ =4 0 f) x4 +5x3 +10x2 +15x+ =9 0
Bµi 6 Gi¶i c¸c ph¬ng tr×nh sau:
5
3 5
2
2
= +
− + +
−
+
x x
x x
x
5
7
2
− +
− +
x x x x
10 4
+
2 2
4
= + +
x
Bµi 7 Gi¶i c¸c hÖ ph¬ng tr×nh sau:
=
−
−
= + +
3
1
2 2
xy y
x
y xy
x
a
= +
= +
10
58
2 2
y x
y x b
−
= +
= +
−
2
13
2 2
y x
y xy x c
= + +
= + +
2
4
2 2
xy y x
y xy x d
Bµi 8 Gi¶i c¸c hÖ ph¬ng tr×nh sau:
a
− = −
=
−
=
−
y
x x y
x
y y x b
4 3
4 3
+
=
−
+
=
−
x y x
y
y x y
x c
2 2
2 2
2 2
2 2
= +
= +
y xy y
x xy x d
3 2
3 2
2 2