Question
Solve the quadratic equation
Solve using the quadratic formula
Solve by completing the square
Solve using the PQ formula
x1=1−15,x2=1+15
Alternative Form
x1≈−2.872983,x2≈4.872983
Evaluate
2x2−28=4x
Move the expression to the left side
2x2−28−4x=0
Rewrite in standard form
2x2−4x−28=0
Substitute a=2,b=−4 and c=−28 into the quadratic formula x=2a−b±b2−4ac
x=2×24±(−4)2−4×2(−28)
Simplify the expression
x=44±(−4)2−4×2(−28)
Simplify the expression
More Steps

Evaluate
(−4)2−4×2(−28)
Multiply
More Steps

Multiply the terms
4×2(−28)
Rewrite the expression
−4×2×28
Multiply the terms
−224
(−4)2−(−224)
Rewrite the expression
42−(−224)
If a negative sign or a subtraction symbol appears outside parentheses, remove the parentheses and change the sign of every term within the parentheses
42+224
Evaluate the power
16+224
Add the numbers
240
x=44±240
Simplify the radical expression
More Steps

Evaluate
240
Write the expression as a product where the root of one of the factors can be evaluated
16×15
Write the number in exponential form with the base of 4
42×15
The root of a product is equal to the product of the roots of each factor
42×15
Reduce the index of the radical and exponent with 2
415
x=44±415
Separate the equation into 2 possible cases
x=44+415x=44−415
Simplify the expression
More Steps

Evaluate
x=44+415
Divide the terms
More Steps

Evaluate
44+415
Rewrite the expression
44(1+15)
Reduce the fraction
1+15
x=1+15
x=1+15x=44−415
Simplify the expression
More Steps

Evaluate
x=44−415
Divide the terms
More Steps

Evaluate
44−415
Rewrite the expression
44(1−15)
Reduce the fraction
1−15
x=1−15
x=1+15x=1−15
Solution
x1=1−15,x2=1+15
Alternative Form
x1≈−2.872983,x2≈4.872983
Show Solution
