Solve the second given equation for x:
x = 7 - y^2
Substitute this expression for x into the first given equation:
(7 - y^2)^2 - y = 7
Expand:
y^4 - 14y^2 + 49 - y = 7
Combine like terms and arrange in standard form:
y^4 - 14y^2 - y + 42 = 0
Use the rational roots theorem (maybe aided by looking at the graph) to
find the roots at y = -3, and y = 2
Use the factor theorem to convert these two roots into factors: (y + 3) (y - 2)
Divide the quartic function by the product of the known factors:
(y^4 - 14y^2 - y + 42) / ((y + 3) (y - 2)) = y^2 - y - 7
Solve this reduced quadratic using the quadratic formula:
y = (1 - √29)/2 and y = (1 + √29)/2
So altogether the four solutions for y are:
y = -3, y = 2, y = (1 - √29)/2 and y = (1 + √29)/2
Substitute these values for y, one at a time, into x + y^2 = 7 and evaluate x:
x = -2, x = 3, x = (√29 - 1)/2, and x = (-1-√29)/2
So the four solutions to the original problem are:
(-2, -3), (3, 2), ((√29 - 1)/2 , (1 - √29)/2) , and ((-1-√29)/2, (1 + √29)/2)
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Verified answer
Solve the second given equation for x:
x = 7 - y^2
Substitute this expression for x into the first given equation:
(7 - y^2)^2 - y = 7
Expand:
y^4 - 14y^2 + 49 - y = 7
Combine like terms and arrange in standard form:
y^4 - 14y^2 - y + 42 = 0
Use the rational roots theorem (maybe aided by looking at the graph) to
find the roots at y = -3, and y = 2
Use the factor theorem to convert these two roots into factors: (y + 3) (y - 2)
Divide the quartic function by the product of the known factors:
(y^4 - 14y^2 - y + 42) / ((y + 3) (y - 2)) = y^2 - y - 7
Solve this reduced quadratic using the quadratic formula:
y = (1 - √29)/2 and y = (1 + √29)/2
So altogether the four solutions for y are:
y = -3, y = 2, y = (1 - √29)/2 and y = (1 + √29)/2
Substitute these values for y, one at a time, into x + y^2 = 7 and evaluate x:
x = -2, x = 3, x = (√29 - 1)/2, and x = (-1-√29)/2
So the four solutions to the original problem are:
(-2, -3), (3, 2), ((√29 - 1)/2 , (1 - √29)/2) , and ((-1-√29)/2, (1 + √29)/2)