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y=x+4

(y+3)/(4)=7x^(2)-x+1
If 
(a,b) is a solution to the system of equations shown and 
a > 0, what is the value of 
a ?

y=x+4 y=x+4 \newliney+34=7x2x+1 \frac{y+3}{4}=7 x^{2}-x+1 \newlineIf (a,b) (a, b) is a solution to the system of equations shown and a>0 , what is the value of a a ?

Full solution

Q. y=x+4 y=x+4 \newliney+34=7x2x+1 \frac{y+3}{4}=7 x^{2}-x+1 \newlineIf (a,b) (a, b) is a solution to the system of equations shown and a>0 a>0 , what is the value of a a ?
  1. Substitute yy in second equation: Substitute the expression for yy from the first equation into the second equation.\newlineSince y=x+4y = x + 4, we can replace yy in the second equation with x+4x + 4.\newline(y+3)/4=7x2x+1(y + 3)/4 = 7x^2 - x + 1 becomes ((x+4)+3)/4=7x2x+1((x + 4) + 3)/4 = 7x^2 - x + 1.
  2. Simplify left side: Simplify the left side of the equation.\newline((x+4)+3)/4=(x+7)/4.((x + 4) + 3)/4 = (x + 7)/4.\newlineNow we have (x+7)/4=7x2x+1.(x + 7)/4 = 7x^2 - x + 1.
  3. Multiply by 44: Multiply both sides of the equation by 44 to eliminate the fraction.\newline4×x+74=4×(7x2x+1)4 \times \frac{x + 7}{4} = 4 \times (7x^2 - x + 1).\newlineThis simplifies to x+7=28x24x+4x + 7 = 28x^2 - 4x + 4.
  4. Rearrange to set to zero: Rearrange the equation to set it to zero and find the values of xx.28x24x+4x7=028x^2 - 4x + 4 - x - 7 = 0.This simplifies to 28x25x3=028x^2 - 5x - 3 = 0.
  5. Solve quadratic equation: Solve the quadratic equation for xx. This is a standard quadratic equation in the form ax2+bx+c=0ax^2 + bx + c = 0. We can use the quadratic formula, x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}, to find the values of xx. Here, a=28a = 28, b=5b = -5, and c=3c = -3.
  6. Calculate discriminant: Calculate the discriminant b24acb^2 - 4ac to determine the nature of the roots.\newlineDiscriminant = (5)24×28×(3) (-5)^2 - 4 \times 28 \times (-3).\newlineDiscriminant = 25+33625 + 336.\newlineDiscriminant = $361.
  7. Calculate roots: Since the discriminant is positive, we have two real roots. Calculate the roots using the quadratic formula.\newlinex=(5)±361228x = \frac{-(-5) \pm \sqrt{361}}{2 \cdot 28}.\newlinex=5±1956x = \frac{5 \pm 19}{56}.
  8. Find possible values for x: Find the two possible values for x.\newlinex=5+1956x = \frac{5 + 19}{56} or x=51956x = \frac{5 - 19}{56}.\newlinex=2456x = \frac{24}{56} or x=1456x = \frac{-14}{56}.\newlinex=37x = \frac{3}{7} or x=14x = \frac{-1}{4}.
  9. Choose positive value for x: Since we are given that a > 0 and aa corresponds to the xx-value in the solution (a,b)(a,b), we choose the positive value for xx.\newlineTherefore, a=37a = \frac{3}{7}.

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