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Toán Lớp 8: Bài 1: Thu gọn ( 2,5đ ) a) 2x.(3x + 1) + (x + 3)(2x – 5) b) ( x + 5)2 – (4x – 1)(4x + 1)

Home/ Toán Lớp 8: Bài 1: Thu gọn ( 2,5đ ) a) 2x.(3x + 1) + (x + 3)(2x – 5) b) ( x + 5)2 – (4x – 1)(4x + 1)

Toán Lớp 8: Bài 1: Thu gọn ( 2,5đ ) a) 2x.(3x + 1) + (x + 3)(2x – 5) b) ( x + 5)2 – (4x – 1)(4x + 1)

Quỳnh Nhi Tháng Chín 13, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: Bài 1: Thu gọn ( 2,5đ )
a) 2x.(3x + 1) + (x + 3)(2x – 5)
b) ( x + 5)2 – (4x – 1)(4x + 1)

Comments ( 2 )

truongankimtrong
13 Tháng Chín, 2022 at 5:52 sáng

Reply

$a$$)$ $2x.(3x + 1) + (x + 3)(2x – 5)$

$=$ $2????(3????+1)+(????+3)(2????−5)$

$=$ $6????^2+2????+(????+3)(2????−5)$

$=$ $6????^2+2????+????(2????−5)+3(2????−5)$

$=$ $6????^2+2????+2????^2−5????+3(2????−5)$

$=$ $6????^2+2????+2????^2−5????+6????−15$

$=$ $6????^2+2????+2????^2+1????−15$

$=$ $8????^2+3????−15$

$b)$ $( x + 5).2 – (4x – 1)(4x + 1)$

$=$ $2x + 10.(8x^2 – 1)$

$=$ $2(x+5).(8x^2 – 1)$
tongtung
13 Tháng Chín, 2022 at 5:52 sáng

Reply

a)

2x(3x+1)+(x+3)(2x-5)

=6x^2+2x+2x^2-5x+6x-15

=(6x^2+2x^2)+(2x-5x+6x)-15

=8x^2+3x-15

b)

(x+5)^2-(4x-1)(4x+1)

=x^2+2.x.5+5^2-[(4x)^2-1^2]

=x^2+10x+25-16x^2+1

=(x^2-16x^2)+10x+(25+1)

=-15x^2+10x+26

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