the lower base of a trapezium is longer than its upper base by 4 cm and its height is 2 times its upper base.If the area of the trapezium is 70 cm^2, find its upper base.
to 001: [x+(x+4)*(2x)]/2=70 isn't correct
- Gary JaiLv 51 decade agoFavorite Answer
Let the upper base be x
x=5 or x=-7 (rejected)
2010-08-23 15:59:29 補充：
Base on the formula of trapezium,[(upper base+lower base)x height]/2 = Area
2010-08-23 16:03:55 補充：
-7 is not an appropriate answer because it is smaller than zero.But for the ''area/perimeter'' cases, answer must be a positive number.
2010-08-23 16:50:32 補充：
To 002: Although you can list the right equation on this question,your step are wrong.
Step3 and 4, 2x^2+4x=70 is not equal to 2x^2-4x-70=0
2010-08-23 16:51:23 補充：
your steps are wrong****
2010-08-23 17:08:42 補充：
Sorry,I don't know why my supplementary content was deleted.
Note that base on the formula of trapezium ,Area=[(lower base+upper base)xheight]/2
And for any ''area or perimeter'' Question, We would like take the positive number while negative number must be rejected.
2010-08-23 17:08:54 補充：
To 002: Although you can list the right equation on this question,your steps are wrong.
In step3 and step 4, 2x^2 + 4x = 70 is not equal to 2x^2 - 4x - 70 = 0.It should be 2x^2+4x-70=0.