math problems don't make sense?

Question

1. (16-7 x^2)+(9-4x+2x^2) my teacher gets the answer -5^2-4x+25 but i get a different answer

2. 2x(x+3)^2 my teacher gets 2x^3+12x^2+18x and i get 2x3+18x

3. 1\5(-5a^2b^3)^2(abc)^2 my teacher gets 5a^6b^8c^2 and i get -1a^6b^8c^2

i've tried so many ways but i can't get her answer!!! please help me

Answer 1

PROBLEM 1:

(16 - 7x²) + (9 - 4x + 2x²)

Here you have an addition, so just remove the parentheses and group like terms:
16 - 7x² + 9 - 4x + 2x²
-7x² + 2x² - 4x + 16 + 9
(-7x² + 2x²) - 4x + (16 + 9)

Now combine these like terms:
-5x² - 4x + 25

PROBLEM 2:
2x(x+3)²

You start by multiplying the squared expression. Remember to use FOIL method (first, outer, inner, last):
2x (x+3)(x+3)
2x (x² + 3x + 3x + 9)
2x (x² + 6x + 9)

Now distribute the 2x:
2x^3 + 12x² + 18x

PROBLEM 3:

(1/5) (-5a² b^3)² (abc)²

Distribute the exponents through:
(1/5) (-5)² (a²)² (b^3)² (a²) (b²) (c²)

Group all the like terms together:
(1/5) (-5)² (a²)² (a²) (b^3)² (b²) (c²)

Now multiply like terms:
(1/5)(25) = 5
(a²)²(a²) = a^4 * a² = a^6
(b^3)² (b²) = b^6 * b² = b^8
(c²) = c²

Putting it all back together:
5 a^6 b^8 c²

Answer 2

1. Your teacher's answer looks right, assuming you mean -5x^2 for the first term. Just combine the like terms, (16+9) + (-7x^2 + 2x^2) + (-4x).

2. Did you expand (x+3)^2 correctly, to get (x^2 + 6x + 9)? Distributing the 2x trough that should give you three terms.

3. There's only one negative sign, and it's within a squared term. So your answer shouldn't have any negatives in the end.

Answer 3

First problem: collect the terms. For x^2, you have -7 + 2, for -5. Teacher scores! For x, you have only -4; teacher scores again! For constant terms, you have 16 + 9 = 25; teacher scores a hat trick! Second problem, multiply out the exponential to get 2x(x*2 + 6x + 9), and when you muliply this out, you again get the teacher's answer. Third problem is done exactly the same way as the second, and is simpler because you are squaring only monomials.

Answer 4

1) 16 - 7x^2 + 9 - 4x + 2x^2
1) (16+9) + (-4x) + (-7x^2 + 2x^2)
1) 25 - 4x - 5x^2

2) 2x(x+3)^2
2) 2x(x^2+6x+9)
2) 2x^3+12x^2+18x

Follow the order of operations!
1) exponents/root
2) parenthesis
3) multiply/divide
4) add/subtract

3) (1/5)(-5a^2b^3)^2*(abc)^2
3) (1/5)(25a^4b^6)*a^2b^2c^2
3) 5a^6b^8c^2

Answer 5

Problem 1:
You have to look at the like terms. 16 and 9 are like terms, so are 7x^2 and 2x^2. 4x is by itself and has no like terms.

16 + 9 = 25
-7x^2 + 2x^2 = -5x^2
And the 4x remains 4x.

So your answer is 25 - 5x^2 - 4x, which is what your teacher got.

Problem 2.

Square what's in the brackets. To make it easier, make it look like:
2x (x + 3) (x + 3)
Use the FOIL method to multiply the brackets together.
x multiplied by x is x^2, x multiplied by 3 is 3x, 3 multiplied by x is again, 3x, and 3 mulitplied by 3 is 9, so you should have:

2x (x^2 + 6x + 9) *remember to combine the like terms (the 3x's)

Now multiply the 2x by what's in the brackets.
2x multiplied by x^2 is 2x^3.
2x multiplied by 6x is 12x^2.
2x multiplied by 9 is 18x.

Maybe you can get the others now. Just remember to combine like terms.

Answer 6

s^2/t^2 = a million so s/t = +-a million so s = +-t then st = -4 so the two s^2 = -4 so s = +-2i and t = +-2i then (s + t) = +-4i or -s^2 = -4 so s = +-2 and t = -+2 then (s + t) = 0 word there are 4 recommendations for s and t for the reason it fairly is an order 4 equation. in case you elect for to forget approximately imaginary numbers the respond is 0, yet truly there are 2 recommendations for what s + t is (ingredient the equation): s^2/t^2 = a million ability s^2 - t^2 = 0 or (s + t)(s - t) = 0 given your difficulty st=-4 s + t = 0 provides the genuine answer and s - t = 0 provides the imaginary answer (word the different sign implication interior the constraint st = -4 shows an imaginary answer for the reason that s - t = 0 is a answer). Sorry for employing imaginaries, even yet it fairly is a factor of the respond.

Answer 7

It would help if you showed us what you did to get those answers.

Like what the guy above me said, you have to combine only terms with the same power. Maybe the rest are just adding/writing problems? Maybe you dropped a negative somewhere? It's hard to tell since you haven't showed us your work.

Answer 8

You cannot combine the squared terms with the terms that have a single variable, they are not like terms.

Ex: 4x+2x^2 <---------These cannot be combined because they are NOT like terms.

Answer 9

i agree