If x = 3 and y = -2, then 2x^2 - y - 3 equals:
A 31
B. 17
C. 35
D. 13
I get 35 but it says the answer is 17...what am I doing wrong? I thought two negatives made a positive.
2007-08-07 20:02:02 · 14 answers · asked by Chris 2 in Science & Mathematics ➔ Mathematics
Odd I just realized it that I was multiplying the 18 by 2 for some odd reason...thanks for helping me realize my mistake.
2007-08-07 20:11:26 · update #1
2x^2-y-3 = 2*9 - (-2) - 3 = 18 + 2 -3 = 17.©
2007-08-07 20:05:44 · answer #1 · answered by Alam Ko Iyan 7 · 1⤊ 3⤋
The answer is 17. Substitute 3 in place of x and -2 for y in the expression 2x^2-y-3. That is,
2(3)^2-(-2)-3
=2*9+2-3
=18+2-3
=20-3
=17!
2007-08-07 20:15:59 · answer #2 · answered by Anonymous · 0⤊ 0⤋
x=3
y= -2
2x^2 - y - 3 = 2(3)^2 - (-2) - 3
Simplifying:
2(9) + 2 - 3
Note that you need to raise 3 to the exponent 2 first before multiplying it to the 2 before it. Otherwise, you'd get 2(3)= 6^2 = 36, which is different. Also, the next term becomes a positive 2; you're right there.
Continuing:
18 + 2 - 3
= 20 - 3
= 17.
There's this PEMDAS rule taught to us to remember the order of operation. It stands for Parenthesis (and other grouping symbols; simplify terms in those first), Exponents (like in this question), Multiplication, Division, Addition, and Subtraction.
Hope that helps!
2007-08-07 20:15:30 · answer #3 · answered by nandemonai 2 · 0⤊ 1⤋
aww ur on the right track but apply the power to the variable BEFORE you multiply it by the coefficient
3 squared = 9 x 2 = 18 + 2 = 20 - 3 = 17 tada
2007-08-07 20:07:20 · answer #4 · answered by Anonymous · 0⤊ 0⤋
since x=3, x^2=9
so the problem can b substituted as,
2*9-(-2)-3=18+2-3=17
your mistake is you took (2X)^2 instead of 2X^2
that is 6^2=36 instead of 2*9=18. so yout got 35 instead of 17
2007-08-07 20:14:54 · answer #5 · answered by renjth k 1 · 0⤊ 0⤋
2(3)^2 - (-2) - 3 start
2(9)- (-2) - 3 square the 3 first
18- (-2) - 3 multiply 2 and 9
18 + 2 -3 the 2 negatives make a positive
20 - 3 then add 2 and 18
17 and lastly, subtract 3
2007-08-07 20:09:16 · answer #6 · answered by sdavila19 3 · 0⤊ 0⤋
(2 x 9) + 2 - 3 = 17
Answer B
2007-08-07 21:44:01 · answer #7 · answered by Como 7 · 1⤊ 0⤋
So then,
2(3)^2 - (-2) - 3
2(9) - (-2) - 3
18 + 2 - 3
20-3= 17
2007-08-07 20:21:35 · answer #8 · answered by Ms. X 4 · 0⤊ 0⤋
if x = 3 and y = -2
2x^2 - y - 3
Then:
2(3)^2 - (-2) - 3
2(9) +2 - 3
18 + 2 - 3
20 - 3
17
You need to remember your order of operations. ^2 comes before multiplying, just like multiplying comes before adding and subtracting.
2007-08-07 20:05:24 · answer #9 · answered by Eagle1 Fox2 7 · 1⤊ 0⤋
oh it's 17 cuz you need to take the power or 3 before you multiply by 2...that's where i messed up the first time.
2007-08-07 20:06:26 · answer #10 · answered by Anonymous · 0⤊ 0⤋