Đáp án:
Giải thích các bước giải:
1) ( x+2 ) ( x+3 )= X^2 + 3x + 2x + 6 = x^2 + 5x +6
3) (x-3y) ( x+y ) = x^2 + xy -3xy - 3y^2= x^2-2xy-3y^2
5 ) (5x-3y)(4x+y)=20x^2+5xy-12xy-3y^2=20x^2 -7xy -3y^2
7) (2a +1 ) (2a+2 +b ) = 4a^2+4a+2ab+2a+2+ab=4𝑎^2+2𝑎𝑏+6𝑎+𝑏+2
9) -(2x-5)(x+2)= (-2x+5)(x+2)= -2x^2 -4x+5x-10=−2𝑥^2+𝑥+10
11) 2x^2 +( x+7) (x-3)= 2x^2 + x^2 -3x+7x-21=3𝑥^2+4𝑥−21
13 ) (x-5)(x+7)-x^2+2=x^2+7x-5x-35-x^2+2=2x-33
15) (x+1) (2x+3) +(3x+2) (x-4)=2x^2+3x+2x+3+3x^2-12x+2x-8=5𝑥^2−5𝑥−5
17) -(x-3) (x+4) +(x+2) ( 1-2x)=-x^2 -4x+3x+12+x-2x^2+x-4x=-3x^2-4x+14
19) -3x^2 +(x-1) (x+3)=-3x^2+x^2+3x-x-3=−2𝑥^2+2𝑥−3
21) 5x^2 - (2x+1) (x-2)= 5x^2-2x^2+4x-x+2=3𝑥^2+3𝑥+2
