( x - 3)( x - 5) + 4 = x^2 - 3x - 5x + 15 + 4 = x^2 - 8x + 19 = x^2 -8x + 16 + 3 = (x - 4)^2 + 3
Vì( x + 4)^2 > = 0 với mọi x => ( x + 4)^2 + 3 lớn hơn bằng 3
VẬy GTNN của bt là 3 khi x + 4 = 0 => x = - 4
Bài 4: Tìm x, biết:
a) 3(2x – 3) + 2(2 – x) = –3 ; b) x(5 – 2x) + 2x(x – 1) = 13 ;
c) 5x(x – 1) – (x + 2)(5x – 7) = 6 ; d) 3x(2x + 3) – (2x + 5)(3x – 2) = 8 ;
e) 2(5x – 8) – 3(4x – 5) = 4(3x – 4) + 11; f) 2x(6x – 2x 2 ) + 3x 2 (x – 4) = 8.
Bài 1:Thực hiện phép tính
a,(5-2x)(x+3)-4x(x+2) b,(3x+1)(x-3)-4(x+2)(x-2)
c,3(x-4)(x+3)+(x-5)(x+3) d,2x(x-4)+(3x-1)(2x-5)
Bài 2:Tìm x biết
a,5x(x+3)-(5x+2)(x+3)=7
b,(3x-1)(3x+2)-9(x+2)(x-2)=10
c,(x+1)(2x-5)+2(3-x)(x+2)=7
d,(1-3x)(x+2)+3x(x-5)=8
Bài1:Rút gọn
a,(4x-5)(3x+2)-(7-3x)(x+2)
b,(-2x+1)(x-5)-3(x-2)(x+1)
c,(x^2-7)(x-5)+(3x^2+5)(2x-4)
d,(x^2+3x-2)(x+4)-4x(x-5)
Bài2:Tìm xbiết
a,(x-4)(x+3)-(x+1)(x-5)=8
b,(3x-2)(x+1)-3x(x+7)=13
c,(x+5)(x-5)-x(x+2)=9
d,(x-1)(x^2+x+1)-x(x^2-3)=1
Tìm x
a.(x+2).(x+3)-(x-2).(x+5) = 0
b. (2x+3).(x-4)+(x-5)(x+2) = (3x-5)(x-4)
c. (3x+2)(2x+9)-(x+2)(6x+1) = x+1-(x-6)
d. 3( 2x-1).(3x-1)-(2x-3).(9x-1)=0
1.Tìm x
a) (x - 5)(x + 5) - (x + 3)^2 + 3 (x - 2)^2 = (x + 1)^2 - (x + 4)(x - 4) +3x^2
b) (2x + 3)^2 + (x - 1)(x + 1) = 5 (x + 2)^2 - (x - 5)(x + 1) + (x + 4)^2
c) (-x + 5)(x - 2) + (x - 7)(x + 7) = (3x + 1)^2 - (3x - 2)(3x + 2)
d) (5x - 1)(x + 1) - 2(x - 3)^2 = (x + 2)(3x - 1) - (x + 4)^2 + (x^2 - x)
2.Rút gọn :
a) A= 3 (x - 1)^2 - (x + 1)^2 + 2(x - 3)(x + 3) - (2x + 3)^2 - (5 - 20x)
b) B= 5x (x - 7)(x + 7) - x (2x - 1)^2 - (x^3 + 4x^2 - 246x) - 175
c) C = -2x (3x + 2)^2 + (4x + 1)^2 + 2 (x^3 + 8x + 3x - 2 ) - (5 - x)
Tìm x biết
A. 2.(3x-1)-5(x-3)-9(2x-4)=24
B. 2x2 +4( x2 -1)=2x (3x+ 1)
C. 2x (5-3x)+2x (3x-5)-3(x-7)=4
Đ. 5x(x+1)-4x(x+2=1-x
Tìm x biết:
a; 3x.(2x+3)-(2x+5x).(3x-2)=8
b;4.(x-1)-3.(x^2-5)_x^2=(x-3)-(x+4)
c; 2.(3x-1).(2x+5)-6.(2x-1).(x+2)=-6
d; 3.(2x-1).(3x-1)-(2x-3.(9x-1)-3=3
tìm x
a,(3x^2-x+1)(x-1)+x^2(4-3x)=5/2
b,4(x+1)^2+(2x-1)^2-8(x-1)(x+1)=11
c,(2x-1)^2+(x+3)^2-5(x+7)(x-7)=0
Tìm x:
a) 3 (2x-1)- 5(x-3)+ 6(3x-4)=24
b) 2x^2 +3(x^2-1) = 5x(x+1)
c) 2x( 5-3x) + 2x(3x-5) -3(-7)=3
d) 3x (x+1) -2x(x+2)=-1-x
tìm x biết
a,5x(x-4)3(x+2)(x-4)=2x(x+1)
b,4x(x+2)-x(8x-5)=10
c,(x+3)(2x-5)=2x(x+4)
d,(3x-2)(x+5)-3x(x+4)=5
e,x(x-3)+2x(x+1)=3(x mũ2-4)
