mvictor wrote:
i got to A..but my main concern, does PEMDAS apply here at all or not?
if not, it needs to be specified so.
PEMDAS - parenthesis, exponents, multiplication, division, addition, subtraction.
exponents come first, so any NEGATIVE integer squared is a positive number...no?
my approach, though lengthy:
list all squares (good to remember squares of the first 20 integers):
1 is positive
4 positive
9 negative
16 positive
25negative
36positive
49negative
64positive
81negative
100positive
121negative
144positive
169negative
196positive
225negative
256positive
289negative
324positive
361negative
400positive
now
400-361 = 39
324-289= 35
256-225=31
196-169=27
144-121=23
100-81=19
64-49=15
36-25=9
16-9=7
and +14=5
now 39+35+31+27+23+19+15+9+7+5
group to be easier:
35+15=50
27+23=50
31+39=70
19+9=28
7+5=12
last digit is 0, so C is out
50+50+70+40=210
A
p.s. surprisingly or not, the sum of all numbers between 1 and 20, inclusive is 20(21)/2 = 210.
Hi,
Quote:
exponents come first, so any NEGATIVE integer squared is a positive number...no?
Yes exponents come first...
But -3^2 is not SQUARE of -IVE integer, it is -IVE of square of positive integer..
so you will first square it and then add -ive sign to it..... \(-3^2= -9\)
If it were (-3)^2, this is what would have been the case given by you.. \((-3)^2 = 9\)Quote:
p.s. surprisingly or not, the sum of all numbers between 1 and 20, inclusive is 20(21)/2 = 210.
If you simplify \(-1^2 + 2^2 - 3^2 + 4^2 - 5^2 + 6^2... +20^2\), you will get 1+2+3+4..+20
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