Live practice

Leading zeros are not significant; zeros between nonzero digits and stated trailing decimal zeros are significant.

Form the required totals explicitly and divide by the full number of observations.

The variance is nonnegative and the reported standard deviation is its positive square root.

Simplify the expression before substitution and preserve one-sided information.

Substitution into the original expression verifies the stated domain and final value.

Use rectangular-coordinate definitions and keep corresponding coordinates aligned.

The final relation satisfies the original coordinate or distance condition, completing the verification.

Translate every condition into an equation and retain exact values throughout the conic calculation.

The last line satisfies the original conditions and supplies every requested part.

Translate every condition into an equation and retain exact values throughout the straight-line calculation.

The last line satisfies the original conditions and supplies every requested part.

Use the sequence definition or geometric-progression formula, keeping the first-term offset explicit.

The displayed substitutions cover every requested part and verify the result against the original data.

Proceed from the given expression and keep every transformation explicit.

The last line satisfies the required domain and establishes the result.

Proceed from the given expression and keep every transformation explicit.

The last line satisfies the required domain and establishes the result.

Proceed from the given expression and keep every transformation explicit.

The last line satisfies the required domain and establishes the result.