a) = [ x( x + 3 ) ][ ( x + 5 )( x - 2 ) ] = ( x2 + 3x )( x2 + 3x - 10 )
= ( x2 + 3x - 5 + 5 )( x2 + 3x - 5 - 5 ) = ( x2 + 3x - 5 )2 - 25 ≥ -25 ∀ x
Dấu "=" xảy ra <=> x2 + 3x - 5 = 0 ( bạn tự giải mình lười quá =)) )
b) = [ ( x - 2 )( x + 4 ) ][ ( x - 3 )( x + 5 ) ] = ( x2 + 2x - 8 )( x2 + 2x - 15 )
Đặt a = x2 + 2x - 8
= a( a - 7 ) = a2 - 7a = ( a2 - 7a + 49/4 ) - 49/4 = ( a - 7/2 )2 - 49/4 = ( x2 + 2x - 23/2 ) - 49/4 ≥ -49/4 ∀ x
Dấu "=" xảy ra <=> x2 + 2x - 23/2 = 0 ( bạn tự giải nốt =) ))
Giải phương trình sau :
a) 11 + 8x – 3 = 5x – 3 + x
b) 2x(x + 2)² - 8x² = 2(x – 2)(x² + 2x + 4)
c) (x + 1)(2x – 3) = (2x – 1)(x + 5)
d) 0,1 – 2(0,5t – 0,1) = 2(t – 2,5) – 0,7
Tìm x
a/ (x-5)(x+5)-(x+3)2+3(x-2)2=(x+1)2-(x-4)(x+4)+3x2
Tìm x
a/ (x-5)(x+5)-(x+3)2+3(x-2)2=(x+1)2-(x-4)(x+4)+3x2
Tìm x, biết :
a) (x-2)3 +6(x+1)2-x3+12=0
b) (x-5) (x+5) - (x+3)2+3(x-2)2=(x+1)2- (x+4)(x-4)+3x2
c) (2x+3)2 +(x-1)(x+1)=5(x+2)2-(x-5)(x+1)+(x+4)
d) (1-3x)2-(x-2)(9x+1)=(3x-4)(3x+4)-9(x+3)2
Giúp mk với ạ, mk cảm ơn !
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)
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
b ,3 (x-2) + 2( 3x - 5) = 10
c, 2x - (3x+1) = 5x-2
d, 3x + 2 = (-5) + 6
bài 3: tìm x , biết:
a)(x+3).(2x-1)-(x-3).(x+1)=0
b)(x+4).(2x-3)-3.(x-2).(x+2)=0
c)x.(x-5).(x+5)-(x+2).(x2-2x+4)=17
Bài 5. Tìm x , biết rằng: a) x(x + 5)(x – 5) – (x + 2)(x2 – 2x + 4) = 3
b) (x – 3)3 – (x – 3)(x2 + 3x + 9) + 9(x + 1)2 = 15
c) (x+5)(x2 –5x +25) – (x – 7) = x3
d) (x+2)(x2 – 2x + 4) – x(x2 + 2) = 4
