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-5x + 4y = 10 and 2x + 9y = -4 Find the value of x.

Sagot :

Answer:

x=-2

Step-by-step explanation:

[tex]a.)[/tex] -5x+4y=10

[tex]b.)[/tex]  2x+9y=-4

Choose one and make it one variable in terms of y.

-5x+4y=10

4y=10+5x

[tex]y=\frac{10+5x}{4}[/tex]

[tex]y= \frac{5}{2} + \frac{5}{4}x[/tex]    →   equation 1

Substitute equation 1 to [tex]b[/tex]

[tex]2x+9(\frac{5}{2} + \frac{5}{4}x)=-4[/tex]

[tex]2x+ \frac{45}{2}+ \frac{45}{4}x=-4[/tex]

[tex]2x+ \frac{45}{4}x=-4 -\frac{45}{2}[/tex]

[tex]\frac{53}{4}x = -\frac{53}{2}[/tex]

[tex]x=-\frac{53}{2}[/tex][tex]/\frac{53}{4}[/tex]

[tex]x=-\frac{4}{2}\\x=-2[/tex]