tìm x biết:
b.4(x+1) ²+(2x-1) ²-8(x-1)(x+1) =11
c.(3x+1) ²+(x+1) ²=10(x-1)(x+1)
d.x(x-1) ²=x ³-2x ²+(x+3)5
Mn giúp mik với ạ. Cám ơn nhìu
tìm x biết:
b.4(x+1) ²+(2x-1) ²-8(x-1)(x+1) =11
c.(3x+1) ²+(x+1) ²=10(x-1)(x+1)
d.x(x-1) ²=x ³-2x ²+(x+3)5
Mn giúp mik với ạ. Cám ơn nhìu
b. `4(x+1)^2+(2x-1)^2-8(x-1)(x+1)=11`
`<=>4(x^2+2x+1)+4x^2-4x+1-8(x^2-1)=11`
`<=>4x^2+8x+4+4x^2-4x+1-8x^2+8=11`
`<=>4x^2+4x^2-8x^2+8x-4x+8+4+1=11`
`<=>4x+13=11`
`<=>4x=-2`
`<=>x=-1/2`
Vậy `x= -1/2`
c. `(3x+1)^2+(x+1)^2=10(x-1)(x+1)`
`<=>9x^2+6x+1+x^2+2x+1=10(x^2-1)`
`<=>9x^2+6x+1+x^2+2x+1-10x^2+10=0`
`<=>9x^2+x^2-10x^2+6x+2x+1+1+10=0`
`<=>8x+12=0`
`<=>8x=-12`
`<=>x=-3/2`
Vậy `x= -3/2`
d. `x(x-1)^2=x^3-2x^2+(x+3).5`
`<=>x(x^2-2x+1)-x^3+2x^2-5x-15=0`
`<=>x^3-2x^2+x-x^3+2x^2+5x-15=0`
`<=>6x-15=0`
`<=>6x=15`
`<=>x=15/6`
Vậy `x=15/6`
Đáp án:
Giải thích các bước giải:
b.
$4(x+1) ²+(2x-1) ²-8(x-1)(x+1) =11$
$4(x² + 2x + 1) + (4x² – 4x + 1) – 8(x² – 1) = 11$
$4x² + 8x + 4 + 4x² – 4x + 1 – 8x² + 8 = 11$
$4x + 13 = 11$
$4x = -2$
$x = \dfrac{-1}{2}$
c.
$(3x+1) ²+(x+1) ²=10(x-1)(x+1)$
$9x² + 6x + 1 + x² + 2x + 1 = 10x² – 10$
$8x + 2 = -10$
$8x = -12$
$x = \dfrac{-3}{2}$
d)
$x(x-1) ²=x ³-2x ²+(x+3)5$
$x(x² – 2x + 1) = x³ – 2x² + 5x + 15$
$x³ – 2x² + x – x³ + 2x² + 5x = 15$
$6x = 15$
$x = \dfrac{15}{6}$