How do you solve y=x^2y=x2 and y=1/2x+5y=12x+5 using substitution?

1 Answer
Jun 30, 2017

Solution: ( x= 5/2 , y= 25/4) or (x= -2 , y=4)(x=52,y=254)or(x=2,y=4)

Explanation:

y= x^2 (1) and y =1/2 x +5 (2)y=x2(1)andy=12x+5(2). Substituting y =1/2 x +5y=12x+5 in equation (1) we get,

x^2 =1/2 x +5 or 2x^2 =x+10 or 2x^2 -x -10 = 0 x2=12x+5or2x2=x+10or2x2x10=0 or

2x^2 -5x +4x -10 = 0 or x(2x-5) + 2(2x-5) =0 2x25x+4x10=0orx(2x5)+2(2x5)=0 or

(2x-5)(x+2) = 0(2x5)(x+2)=0. Either 2x-5 = 0 or 2x= 5 :. x=5/2 or

x+2=0 :. x=-2 :. x =5/2 or x= -2

When x=5/2 ; y= 1/2*5/2 +5 = 5/4+5 =25/4 ;

When x=-2 ; y= 1/2*(-2) +5 = -1+5 =4 ;

Solution: ( x= 5/2 , y= 25/4) or (x= -2 , y=4) [Ans]