Q. y=x+44y+3=7x2−x+1If (a,b) is a solution to the system of equations shown and a>0, what is the value of a ?
Substitute y in second equation: Substitute the expression for y from the first equation into the second equation.Since y=x+4, we can replace y in the second equation with x+4.(y+3)/4=7x2−x+1 becomes ((x+4)+3)/4=7x2−x+1.
Simplify left side: Simplify the left side of the equation.((x+4)+3)/4=(x+7)/4.Now we have (x+7)/4=7x2−x+1.
Multiply by 4: Multiply both sides of the equation by 4 to eliminate the fraction.4×4x+7=4×(7x2−x+1).This simplifies to x+7=28x2−4x+4.
Rearrange to set to zero: Rearrange the equation to set it to zero and find the values of x.28x2−4x+4−x−7=0.This simplifies to 28x2−5x−3=0.
Solve quadratic equation: Solve the quadratic equation for x. This is a standard quadratic equation in the form ax2+bx+c=0. We can use the quadratic formula, x=2a−b±b2−4ac, to find the values of x. Here, a=28, b=−5, and c=−3.
Calculate discriminant: Calculate the discriminant b2−4ac to determine the nature of the roots.Discriminant = (−5)2−4×28×(−3).Discriminant = 25+336.Discriminant = $361.
Calculate roots: Since the discriminant is positive, we have two real roots. Calculate the roots using the quadratic formula.x=2⋅28−(−5)±361.x=565±19.
Find possible values for x: Find the two possible values for x.x=565+19 or x=565−19.x=5624 or x=56−14.x=73 or x=4−1.
Choose positive value for x: Since we are given that a > 0 and a corresponds to the x-value in the solution (a,b), we choose the positive value for x.Therefore, a=73.
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