5*11+7*4 show work plz
1 answer:
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Answer:
{x,y} = {6/5,23/10}
Step-by-step explanation:
[1] 7x + 2y = 13
[2] 4x + 4y = 14 <---------- linear equations given
Graphic Representation of the Equations : PICTURE
2y + 7x = 13 4y + 4x = 14
Solve by Substitution :
// Solve equation [2] for the variable y
[2] 4y = -4x + 14
[2] y = -x + 7/2
// Plug this in for variable y in equation [1]
[1] 7x + 2•(-x +7/2) = 13
[1] 5x = 6
// Solve equation [1] for the variable x
[1] 5x = 6
[1] x = 6/5
// By now we know this much :
x = 6/5
y = -x+7/2
// Use the x value to solve for y
y = -(6/5)+7/2 = 23/10
// Plug this in for variable y in equation [1]
[1] 7x + 2•(-x +7/2) = 13
[1] 5x = 6
// Solve equation [1] for the variable x
[1] 5x = 6
[1] x = 6/5
// By now we know this much :
x = 6/5
y = -x+7/2
// Use the x value to solve for y
y = -(6/5)+7/2 = 23/10
Answer:
2 solutions
Step-by-step explanation:
I like to use a graphing calculator to find solutions for equations like these. The two solutions are ...
- x = 1
- x = 4
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To solve this algebraically, it is convenient to subtract 2x-7 from both sides of the equation:
3x(x -4) +5 -x -(2x -7) = 0
3x^2 -12x +5 -x -2x +7 = 0 . . . . . eliminate parentheses
3x^2 -15x +12 = 0 . . . . . . . . . . . . collect terms
3(x -1)(x -4) = 0 . . . . . . . . . . . . . . . factor
The values of x that make these factors zero are x=1 and x=4. These are the solutions to the equation. There are two solutions.
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<em>Alternate method</em>
Once you get to the quadratic form, you can find the number of solutions without actually finding the solutions. The discriminant is ...
d = b^2 -4ac . . . . where a, b, c are the coefficients in the form ax^2+bx+c
d = (-15)^2 -4(3)(12) = 225 -144 = 81
This positive value means the equation has 2 real solutions.
