\(a.\left(x-2\right)^2-x\left(x-6\right)=\left(x^2-4x+4\right)-x^2+6x=x^2-4x+4-x^2+6x=4+2x \)
Bài 5:
a. (x - 1)(x + 4) - x(x + 2) = 5
<=> x2 + 4x - x - 4 - x2 - 2x = 5
<=> x2 - x2 + 4x - x - 2x = 5 + 4
<=> x = 9
b. (x - 2)2 - x(x + 5) = 3
<=> x2 - 4x + 4 - x2 - 5x = 3
<=> x2 - x2 - 4x - 5x = 3 - 4
<=> -9x = -1
<=> x = \(\dfrac{-1}{-9}=\dfrac{1}{9}\)
Bài 4:
a) \(\left(x-2\right)^2-x\left(x-6\right)=x^2-4x+4-x^2+6x=2x+4\)
b) \(\left(x+1\right)^2-\left(x-1\right)\left(x-2\right)=x^2+2x+1-x^2+3x-2=5x-1\)
c) \(\left(a-b\right)^2+3a\left(a+b\right)=a^2-2ab+b^2+3a^2+3ab=4a^2+ab+b^2\)
d) \(\left(a+b\right)^2-3ab\left(a-b\right)=a^2+2ab+b^2-3a^2b+3ab^2\)
Bài 5:
a) \(\left(x-1\right)\left(x+4\right)-x\left(x+2\right)=5\)
\(\Leftrightarrow x^2+3x-4-x^2-2x=5\)
\(\Leftrightarrow x=9\)
b) \(\left(x-2\right)^2-x\left(x+5\right)=3\)
\(\Leftrightarrow x^2-4x+4-x^2-5x=3\)
\(\Leftrightarrow-9x=-1\Leftrightarrow x=\dfrac{1}{9}\)
bài 4
a)(x-2)^2-x(x-6)
=x^2-4x+4-x^2+6x
b)(x+1)^2-(x-1)(x-2)
=x^2+2x+1-(x^2-2x-x+2)
=x^2+2x+1-x^2+2x-2
=4x-1
c)(a-b)^2+3a(a+b)
=a^2-2ab+b^2+3a^2+3ab
=4a^2+b^2-ab
d)(a+b)^2-3ab(a-b)
=a^2+2ab+b^2-3a^2b+3ab^2
=a^2+b^2-3a^2b+3ab^2+2ab
mink cần gấp ạ
