f.2代入數唔識=__=(20分)

只要將題目中給出的變數值代入就可以了

1) 3x + 5 = 3 * 6 + 5 = 23

2) y^2 - 3y + 15

= (-2)^2 - 3(-2) + 15

= 4 + 6 + 15

= 25

3) )5a^3 + 2a^2 - 4a + 10

= 5(3)^3 + 2(3)^2 - 4(3) + 10

= 135 + 18 - 12 + 10

= 151

4) m^2/2 + 6m -1/2

= (-5)^2/2 + 6(-5) - 1/2

= 25/2 - 30 - 1/2

= -18

1)3x+5 (x=6)
=3(6)+5
=18+5
=23

2)y^2-3y+15 (y= -2)
=(-2)^2-3(-2)+15
=4+6+15
=25

3)5a^3+2a^2-4a+10 (a=3)
=5(3)^3+2(3)^2-4(3)+10
=5(27)+2(9)-4(3)+10
=135+18-12+10
=151

4)m^2/2+6m-1/2 (m=-5)
=(-5)^2/2+6(-5)-1/2
=25/2-30-1/2
=25/2-31/2
=(25-31)/2
=-6/2
=-3

只要將括號入面個數代翻入去個未知數就得，記住好似第2題咁，未知數係負數ge話，要加括號，要成個負數ge次方，唔好變成 -2^2 = -4 ,負數ge次方如果個次方係雙數就變正數，單數就變負數~