Question
Find the roots
z1=−51−1086i,z2=−51+1086i
Alternative Form
z1≈−0.2−0.927362i,z2≈−0.2+0.927362i
Evaluate
10z2+4z+9
To find the roots of the expression,set the expression equal to 0
10z2+4z+9=0
Substitute a=10,b=4 and c=9 into the quadratic formula z=2a−b±b2−4ac
z=2×10−4±42−4×10×9
Simplify the expression
z=20−4±42−4×10×9
Simplify the expression
More Steps

Evaluate
42−4×10×9
Multiply the numbers
More Steps

Multiply the terms
4×10×9
Multiply the terms
40×9
Multiply the numbers
360
42−360
Evaluate the power
16−360
Subtract the numbers
−344
z=20−4±−344
Simplify the radical expression
More Steps

Evaluate
−344
Evaluate the power
344×−1
Evaluate the power
344×i
Evaluate the power
More Steps

Evaluate
344
Write the expression as a product where the root of one of the factors can be evaluated
4×86
Write the number in exponential form with the base of 2
22×86
The root of a product is equal to the product of the roots of each factor
22×86
Reduce the index of the radical and exponent with 2
286
286×i
z=20−4±286×i
Separate the equation into 2 possible cases
z=20−4+286×iz=20−4−286×i
Simplify the expression
More Steps

Evaluate
z=20−4+286×i
Divide the terms
More Steps

Evaluate
20−4+286×i
Rewrite the expression
202(−2+86×i)
Cancel out the common factor 2
10−2+86×i
Use b−a=−ba=−ba to rewrite the fraction
−102−86×i
Simplify
−51+1086i
z=−51+1086i
z=−51+1086iz=20−4−286×i
Simplify the expression
More Steps

Evaluate
z=20−4−286×i
Divide the terms
More Steps

Evaluate
20−4−286×i
Rewrite the expression
202(−2−86×i)
Cancel out the common factor 2
10−2−86×i
Use b−a=−ba=−ba to rewrite the fraction
−102+86×i
Simplify
−51−1086i
z=−51−1086i
z=−51+1086iz=−51−1086i
Solution
z1=−51−1086i,z2=−51+1086i
Alternative Form
z1≈−0.2−0.927362i,z2≈−0.2+0.927362i
Show Solution
