Question

Michiko claims that to solve the system of linear equations 15 x + 8 y = 1 and 21 x + 4 y = negative 13, instead of multiplying the second equation by –2 and then adding the equations, she could multiply the second equation by 2 and then subtract the second equation from the first equation. Which statement is correct? Michiko is right for this system of linear equations, but her method will not work for other systems of linear equations. Michiko is right for this system of linear equations, and her method will also work for other systems of linear equations. Michiko is wrong because her method will give the opposite of the correct value for x for any system of linear equations. Michiko is wrong because her method will give the opposite of the correct value for y for any system of linear equations.

Answer 1

Explanation:

15 x + 8 y = 1

21 x + 4 y = - 13

Method 1: multiplying the second equation by –2 and then adding the equations

15x + 8y = 1

-42x - 8y = 26

-------------------------------( add side by side)

-27x + 0 = 27

so x = -1 and y= 2

Method 2: multiply the second equation by 2 and then subtract the second equation from the first equation

15 x + 8 y = 1

42 x + 8 y = - 26

---------------------------- ( subtract)

15 x - 42x + 8y - 8y = 1 - (-26)

-27 x + 0 = 1 + 26

-27x = 27

or x = -1 and y =2

So we choose: " Michiko is right for this system of linear equations, and her method will also work for other systems of linear equations."

Car add A is the same with subtract -A.

Answer 2

b

Explanation: