Question

MEDAL! I need help solving this.
y=x^2 +2x
y=3x+20

Answer 1

Set x or y equal to 0

Answer 2

Doesn't matter which

Answer 3

Combine them or set one variable to 0

Answer 4

Preferably y

Answer 5

ok

Answer 6

?

Answer 7

y = y
x^2 + 2x = 3x + 20 as each is equal to y. Now use algebra.
x^2 -x -20 = 0 Factor and solve.

Answer 8

How do I do that? Like this? 0=3x+20?

Answer 9

(x - 5) (x + 4) = 0

Answer 10

Solve for x, then get y.

Answer 11

Ok...I'm still confused though. Sorry

Answer 12

Re read my post, it is lined out in a step by step manner.

Answer 13

First does, the y = y seem reasonable?

Answer 14

Yes

Answer 15

Given y= x^2 + 2x and y = 3x + 20 if y=y then we must also have:
x^2 + 2x = 3x + 20 that has to be true as y=y ..........agree?

Answer 16

Ohhh yes I see now.

Answer 17

Now we isolate by subtracting 3x from both sides giving us:
x^2 - x = 20 Now to form a quadratic equation in standard form Subtract 20 from both sides giving us: x^2 - x -20 =0

Have you solved quadratics before?

Answer 18

Oh ok. And Yes but I never realy got the concept.

Answer 19

? You just lost me again sorry...

Answer 20

y = x^2 + 2x
y= 5^2 + 2(5) = 25 + 10 = 35 (5,35)
y = -4^2 + 2(-4) = 16 - 8 = 8 (-4, 8)

y = 3x + 20
y = 3(5) + 20 = 35 (5,35)
y= 3(-4) + 20 = -12 + 20 = 8 (-4,8) the same for both equations two sets of answers

Answer 21

I did have an error:
Here is the way it should read:

The three most common methods are, quadratic formula, completing the square and factoring.
Factoring is the way to go on this one, as it easily factors into:
(x-5)(x+r) = 0
x - 5 = 0 so that x=5
x + 4 = 0 so that x= -4 Now substitute those values for x and see what y can be.

What part of that has caused confusion on your part?

Answer 22

Where did the 4 and come frome as well as the r?

Answer 23

and 5*

Answer 24

Darn the error is still there:
The three most common methods are, quadratic formula, completing the square and factoring.
Factoring is the way to go on this one, as it easily factors into:
(x-5)(x+4) = 0
x - 5 = 0 so that x=5
x + 4 = 0 so that x= -4 Now substitute those values for x and see what y can be.
That fixed, the "r" was supposed to be a 4 lol.

Answer 25

The r should of been a 4 so that
X^2 - 1x - 20 = 0 is when factored is
(x - 5)(x + 4) = 0

Answer 26

Ohh I get it now.