F2 MATHS

2007-01-08 12:58 am
1) = mean identity , ^ mean 二次方 , *mean 三次方

If Ax(x-1)(x+2)+Bx(x-1)+Cx+D = 5x* + 3X^ - 10x + 6 , find the values of A,B,C,D.

Use identities to find the values of the following.

2) 54(46)

3) 102^ - 16(108) + 63
更新1:

3) 108^ - 16(108) + 63

回答 (3)

2007-01-08 1:20 am
✔ 最佳答案
Ax(x-1)(x+2) + Bx(x-1) + Cx + D = 5x* + 3X^ - 10x + 6
Ax(x^ + x -2) + B(x^ - x) + Cx + D = 5x* + 3X^ - 10x + 6
A(x* + x^ - 2x) + B(x^ - x) + Cx + D = 5x* + 3X^ - 10x + 6
Ax* + (A + B)x^ + (-2A - B + C)x + D = 5x* + 3X^ - 10x + 6

By comparing the coefficients,

A = 5
A + B = 3, therefore B = -2
-2A - B + C = -10, therefore C = -2
D = 6

54(46)
=(50 + 4)(50 - 4)
=50^ - 4^
=2500 - 16
=2484

108^ - 16(108) + 63
=(108 - 9)(108 - 7)
=99(101)
=9999

P.S. The symbols are the same as the question given.
2007-01-08 9:32 pm
1)Ax(x-1)(x+2)+Bx(x-1)+Cx+D = 5x³ + 3X² - 10x + 6

Ax³-Ax²+Bx²-Bx+Cx+D=5x³ + 3X² - 10x + 6

A=5 B=8 C=-2 D=6
-------------------------------------------------------------------------------------------------------
2)54(46)

=(50+4)(50-4)

=2500+200-200-16

=2516
-------------------------------------------------------------------------------------------------------
3)102² - 16(108) + 63

=102² - (62-46)(62+46) + 63

=102² - (3844+2852-2852-2116) + 63

=102² - 1728 + 63

=(100+2)² - 1728 + 63

=(10000+200-200+4) - 1728 + 63

=10004 - 1728 + 63

=8339
參考: 數學能手Me
2007-01-08 1:18 am
1)A=5 B=-2 C=-10 D=6
2) 2484
3) 9999
參考: Me


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