2x + (-61) - (21 - 61) = 2x - 21 + (61 - 61) = 2x - 21

2x+(-61)-(21-61)=2x-61-21+61=2x-(61-61)-21=2x-21

Cảm ơn

a ) 2x + (-61)-(21-61)

= 2x - 61 - 21 + 61

= 2x - 21

b) (-3-x+5) +3

= -3 - x + 5 + 3

= -x + 5

a) 2x + (-61) -21+61

= 2x - 21

b) (-3-x+5) +3

= -3+3-x+5

= -x+5

a) \(2x+\left(-61\right)-\left(21-61\right)\)

\(=2x-61-\left(-40\right)\)

\(=2x-61+40\)

\(=2x+\left(-61+40\right)\)

\(=2x-21\)

b) \(\left(-3-x+5\right)+3\)

\(=2-x+3\)

\(=-x+\left(2+3\right)\)

\(=5-x\)

a) A = 2x^2 + 2y^2

a, \(A=\left(x-y\right)^2+\left(x+y\right)^2\)

\(=x^2-2xy+y^2+x^2+2xy+y^2\)

\(=2x^2+2y^2\)

a) \(A=\left(x-y\right)^2+\left(x+y\right)^2\\ =x^2-2xy+y^2+x^2+2xy+y^2=2x^2+2y^2\)

b) \(B=\left(2x-1\right)^2-2\left(2x-3\right)^2+4\\ =4x^2-4x+1-2\left(4x^2-12x+9\right)+4\\ =4x^2-4x+1-8x^2+24x-18+4\)

    \(=-4x^2+20x-13\)

a . 21/70 = 3/10 ; 56/96 = 7/12 ; 60/72 = 15/18

Mình chỉ làm tới đây thôi .

Bài 1:

a, \(\left(x-y+2z\right)^2=x^2+y^2+4z^2-2xy-4yz+4zx\)

b, \(\left(2x-3\right)\left(2x+3\right)\left(4x^2+9\right)=\left(4x^2-9\right)\left(4x^2+9\right)=16x^4-81\)

Lời giải:

a.

$=-37-x-23+15=-x-(37+23)+15=-x-60+15=-x-(60-15)=-x-45$

b.

$=176-176+x-42=0+x-42=x-42$

c.

$=1270-1270+2x+31=0+2x+31=2x+31$

d.

$=2x-141-231+461=2x-(141+231)+461=2x-372+461$

$=2x+(461-372)=2x+89$