SOLUTION: Here's the question and part of the solution.
How many ordered pairs (x,y) satisfy this system of equations:
x = 2y + 5
y = (2x-3)(x+9)
Here's part of the solution:
Step 1
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-> SOLUTION: Here's the question and part of the solution.
How many ordered pairs (x,y) satisfy this system of equations:
x = 2y + 5
y = (2x-3)(x+9)
Here's part of the solution:
Step 1
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Question 978100: Here's the question and part of the solution.
How many ordered pairs (x,y) satisfy this system of equations:
x = 2y + 5
y = (2x-3)(x+9)
Here's part of the solution:
Step 1. Substitute y in the 2nd equation into the first equation to get x = 2((2x-3)(x+9)) + 5
Step 2. The above = 4x^2 + 30x - 54
Step 3. The solution says this can be rewritten as: 4x^2 + 29x -54 = 0.
Here are my problems: What happened to the 5 on the end of the equation in Step 1? Where did the 29 come from in Step 3?
Thank you for any help?
Helen Found 3 solutions by josgarithmetic, Boreal, MathTherapy:Answer by josgarithmetic(39616) (Show Source):
Find the solutions for y, which might be none, or one, or two of them.
I CHOSE to make the substitution for x instead of for y. You could just as well make the sub for y as you may have wanted. My view is that the subst for x is easier to use.
What you actually tried to do is tougher, and may be more work.
You can put this solution on YOUR website! (2x-3)(x+9)= 2x^2+15x-27
2 times that is 4x^2+30x-54
but x=4x^2-30x-54] ;; original equation was x=2y+5
subtract x from both sides
0=4x^2+29x-49
You are right about the 5. That has to be carried through.
You can put this solution on YOUR website!
Here's the question and part of the solution.
How many ordered pairs (x,y) satisfy this system of equations:
x = 2y + 5
y = (2x-3)(x+9)
Here's part of the solution:
Step 1. Substitute y in the 2nd equation into the first equation to get x = 2((2x-3)(x+9)) + 5
Step 2. The above = 4x^2 + 30x - 54
Step 3. The solution says this can be rewritten as: 4x^2 + 29x -54 = 0.
Here are my problems: What happened to the 5 on the end of the equation in Step 1? Where did the 29 come from in Step 3?
Thank you for any help?
Helen
x = 2y + 5 ----- eq (i)
y = (2x - 3)(x + 9) ----- eq (ii)
x = 2[(2x - 3)(x + 9)] + 5 ------- Substituting (2x - 3)(x + 9) for y in eq (i)
(