Toán Lớp 8: rút gọn 5,E=(2x-5) ²-(2x+5) ²+40x-1 6,F=(3x-2y) ²+(3x+2y) ²-18x ²-8y ²+1 7,G=(2+x) ²-(2-x) ²-8x+3 cần câu trả lời đg vote 5 sao
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Toán Lớp 8: rút gọn 5,E=(2x-5) ²-(2x+5) ²+40x-1 6,F=(3x-2y) ²+(3x+2y) ²-18x ²-8y ²+1 7,G=(2+x) ²-(2-x) ²-8x+3 cần câu trả lời đg vote 5 sao
Comments ( 1 )
E = ( 2x – 5 )^2 – ( 2x + 5 )^2 + 40x – 1
= ( 2x – 5 – 2x – 5 ) . ( 2x – 5 + 2x + 5 ) + 40x – 1
= – 10 . 4x + 40x – 1
= – 40x + 40x – 1
= -1
6)
F = ( 3x – 2y )^2 + ( 3x + 2y )^2 – 18x^2 – 8y^2 + 1
= 9x^2 – 12xy + 4y^2 + 9x^2 + 12xy + 4y^2 – 18x^2 – 8y^2 + 1
= 18x^2 + 8y^2 – 18x^2 – 8y^2 + 1
=1
7)
G= ( 2 + x )^2 – ( 2 – x )^2 – 8x + 3
= ( 2 + x – 2 + x ) . ( 2 + x + 2 – x ) – 8x + 3
= 2x . 4 – 8x + 3
= 8x – 8x + 3
= 3