How do you solve the following system using substitution?: 5x+2y=-4, -3x+y=20

2 Answers
Jim G.
May 7, 2018

(x,y)to(-4,8)

Explanation:

5x+2y=-4to(1)

-3x+y=20to(2)

"rearrange equation "(2)" to express y in terms of x"

"add "3x" to both sides"

rArry=20+3xto(3)

color(blue)"substitute "y=20+3x" into equation "(1)

5x+2(20+3x)=-4larr"distribute"

rArr5x+40+6x=-4

rArr11x+40=-4

"subtract 40 from both sides"

rArr11x=-44

"divide both sides by 11"

rArrx=(-44)/11=-4

"substitute "x=-4" into equation "(3)

rArry=20-12=8

"the point of intersection "=(-4,8)

Narad T.
May 7, 2018

The solutions are {x=-4 ; y=8}

Explanation:

The equations are

{(5x+2y=-4),(-3x+y=20):}

<=>, {(5x+2y=-4),(y=3x+20):}

<=>, {(5x+2(3x+20)=-4),(y=3x+20):}

<=>, {(11x+40=-4),(y=3x+20):}

<=>, {(11x=-44),(y=3x+20):}

<=>, {(x=-4),(y=3xx-4+20=8):}

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