BÀI TẬP
Bài 1: Làm tính nhân:
a) 2x. (x- 7x -3)
b) (-2x + y -7xy). 4xy
c(-5x’). (2x²+3x-5)
e)(x -2x+3). (x-4)
g) ( 25x + 10xy+ 4y).( 5x-2y)
Bài 2: Thực hiện phép tính:
d) (2x – – xy+ y),(-3x’)
) ( 2x -3x -1). (5x+2)
h) ( 5x-x² + 2x – 3).( 4x -x +2)
a) ( 2x + 3y )
c)
) ( 3x – 2y)’ ;
h) (x+4) ( x² – 4x + 16) h)(x-3y)(x² + 3xy +9y)
1)(x- 1) (x + 3)
m) (x – -y)²
Bài 3: Tính nhanh:
a) 2004 – 16;
c) 10,2.9,8-9,8.0,2 + 10,22 -10,2.0,2
e) 99 +1+3(99 +99)
g) 20,03. 45 + 20,03.47+20,03. 8
BÀI TẬP Bài 1: Làm tính nhân: a) 2x. (x- 7x -3) b) (-2x + y -7xy). 4xy c(-5x’). (2x²+3x-5) e)(x -2x+3). (x-4) g) ( 25x + 10xy+ 4y).( 5x-2y) Bài 2: Thự
By Madeline
Đáp án:
Giải thích các bước giải::
a) 2x(x−7x−3)2x(x−7x−3) =2x(−6x−3)=−12x2−6x=2x(−6x−3)=−12×2−6x.
b) (−2x+y−7xy).4xy(−2x+y−7xy).4xy =−8x2y+4xy2−28x2y2=−8x2y+4xy2−28x2y2
c) (−5x)(2x2+3x−5)(−5x)(2×2+3x−5)=−10x3−15x2+25x=−10×3−15×2+25x.
e) (x−2x+3)(x−4)=(−x+3)(x−4)(x−2x+3)(x−4)=(−x+3)(x−4)
=−x2+4x+3x−12=−x2+7x−12=−x2+4x+3x−12=−x2+7x−12
g) (25x+10xy+4y)(5x−2y)(25x+10xy+4y)(5x−2y)
=125x2−50xy+50x2y−20xy2+20xy−8y2=125x2−30xy+50x2y−20xy2−8y2=125×2−50xy+50x2y−20xy2+20xy−8y2=125×2−30xy+50x2y−20xy2−8y2
Bài 2:
d) (2x−xy+y)(−3x)=−6x2+3x2y−3xy(2x−xy+y)(−3x)=−6×2+3x2y−3xy
e) (2x−3x−1)(5x+2)=(−x−1)(5x+2)(2x−3x−1)(5x+2)=(−x−1)(5x+2)
=−5x2−2x−5x−2=−5x2−7x−2=−5×2−2x−5x−2=−5×2−7x−2
h) (5x−x2+2x−3)(4x−x+2)=(−x2+7x−3)(3x+2)(5x−x2+2x−3)(4x−x+2)=(−x2+7x−3)(3x+2)
=−3x3−2x2+21x2+14x−9x−6=−3x3+19x2+5x−6=−3×3−2×2+21×2+14x−9x−6=−3×3+19×2+5x−6
h) (x+4)(x2−4x+16)=x3+43=x3+64(x+4)(x2−4x+16)=x3+43=x3+64h) (x−3y)(x2+3xy+9y2)=x3−(3y)3=x3−27y3(x−3y)(x2+3xy+9y2)=x3−(3y)3=x3−27y3.
1) (x−1)(x+3)=x2+3x−x−3=x2+2x−3(x−1)(x+3)=x2+3x−x−3=x2+2x−3.
Bài 3:
a) 2004−16=2004−4−12=2000−12=19882004−16=2004−4−12=2000−12=1988
b) 10,2.9,8−9,8.0,2+10,22−10,2.0,2
Bài 1:
a) \(2x\left( {x – 7x – 3} \right)\) \( = 2x\left( { – 6x – 3} \right) = – 12{x^2} – 6x\).
b) \(\left( { – 2x + y – 7xy} \right).4xy\) \( = – 8{x^2}y + 4x{y^2} – 28{x^2}{y^2}\)
c) \(\left( { – 5x} \right)\left( {2{x^2} + 3x – 5} \right)\)\( = – 10{x^3} – 15{x^2} + 25x\).
e) \(\left( {x – 2x + 3} \right)\left( {x – 4} \right) = \left( { – x + 3} \right)\left( {x – 4} \right)\)
\( = – {x^2} + 4x + 3x – 12 = – {x^2} + 7x – 12\)
g) \(\left( {25x + 10xy + 4y} \right)\left( {5x – 2y} \right)\)
\(\begin{array}{l} = 125{x^2} – 50xy + 50{x^2}y – 20x{y^2} + 20xy – 8{y^2}\\ = 125{x^2} – 30xy + 50{x^2}y – 20x{y^2} – 8{y^2}\end{array}\)
Bài 2:
d) \(\left( {2x – xy + y} \right)\left( { – 3x} \right) = – 6{x^2} + 3{x^2}y – 3xy\)
e) \(\left( {2x – 3x – 1} \right)\left( {5x + 2} \right) = \left( { – x – 1} \right)\left( {5x + 2} \right)\)
\( = – 5{x^2} – 2x – 5x – 2 = – 5{x^2} – 7x – 2\)
h) \(\left( {5x – {x^2} + 2x – 3} \right)\left( {4x – x + 2} \right) = \left( { – {x^2} + 7x – 3} \right)\left( {3x + 2} \right)\)
\(\begin{array}{l} = – 3{x^3} – 2{x^2} + 21{x^2} + 14x – 9x – 6\\ = – 3{x^3} + 19{x^2} + 5x – 6\end{array}\)
h) \(\left( {x + 4} \right)\left( {{x^2} – 4x + 16} \right) = {x^3} + {4^3} = {x^3} + 64\)h) \(\left( {x – 3y} \right)\left( {{x^2} + 3xy + 9{y^2}} \right) = {x^3} – {\left( {3y} \right)^3} = {x^3} – 27{y^3}\).
1) \(\left( {x – 1} \right)\left( {x + 3} \right) = {x^2} + 3x – x – 3 = {x^2} + 2x – 3\).
Bài 3:
a) \(2004 – 16 = 2004 – 4 – 12 = 2000 – 12 = 1988\)
b) \(10,2.9,8 – 9,8.0,2 + 10,22 – 10,2.0,2\)
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