Question

Mọi người giúp mình nha

Giải chi tiết nha

Câu 1 . Tìm x biết

a, (x-1)^2-(x+1)^2=3

b, (x-2)(x+2)-(x-3)^2=5x-1

c, x(x-2)-(x+3)^2-x=4

d, 6x(x-1)-5(x-2)^2-x(x-3)=4

Answer 1

a/ (x-1)² - (x+1)² = 3

<=> (x-1-x-1)(x-1+x+1) = 3

<=> - 2 . 2x = 3

<=> -4x = 3 <=> x = -3/4

KL: x = -3/4

b/ (x-2)(x+2) - (x-3) ^2 = 5x - 1

<=> x² - 4 - x² + 6x - 9 = 5x - 1

<=> 6x - 5x = -1 + 4 + 9

<=> x = 12

KL: x= 12

c/ x(x-2) - (x+3)² - x = 4

<=> x² - 2x - x² - 6x - 9 - x = 4

<=> -9x = 4 + 9

<=> x = -13/9

KL: x= -13/9

d/ 6x(x-1) - 5(x-2)² - x(x - 3) = 4

<=> 6x² - 6x - 5(x² - 4x + 4) - x² - 3x = 4

<=> 6x² - 6x - 5x² + 20x - 20 -x² - 3x = 4

<=> 11x = 24

<=> x = 24/11

KL: x = 24/11

Answer 2

a)

\(\left(x-1\right)^2-\left(x+1\right)^2=3\\ \Leftrightarrow-2.2x=3\\ \Leftrightarrow-4x=3\\ \Leftrightarrow x=-\dfrac{4}{3}\)

Vậy...

b)

\(\left(x-2\right)\left(x+2\right)-\left(x-3\right)^2=5x-1\\ \Leftrightarrow x^2-4-\left(x^2-6x+9\right)=5x-1\\ \Leftrightarrow x^2-4-x^2+6x-9=5x-1\\ \Leftrightarrow-13+6x=5x-1\\ \Leftrightarrow6x-5x=-1+13\\ \Leftrightarrow x=12\)

Vậy...

Answer 3

\(c)x\left(x-2\right)-\left(x+3\right)^2-x=4\\ \Leftrightarrow x^2-2x-\left(x^2+6x+9\right)-x=4\\ \Leftrightarrow x^2-2x-x^2-6x-9-x=4\\ \Leftrightarrow-9x-9=4\\ \Leftrightarrow-9x=4+9\\\Leftrightarrow-9x=13\\ \Leftrightarrow x=-\dfrac{13}{9} \)

Vậy...

\(d)6x\left(x-1\right)-5\left(x-2\right)^2-x\left(x-3\right)=4\\ \Leftrightarrow6x^2-6x-5\left(x^2-4x+4\right)-x^2+3x=4\\ \Leftrightarrow6x^2-6x-5x^2+20x-20-x^2+3x=4\\ \Leftrightarrow17x-20=4\\ \Leftrightarrow17x=4+20\\ \Leftrightarrow17x=24\\ \Leftrightarrow x=\dfrac{24}{17}\)

Vậy...