The word “algebra” is enough to make most people’s inner child recoil in horror. The thought of using a geometric formula might summon a panic attack.

Unless your teacher was Maclear “Mac” Jacoby Jr.

“Mac’s classes were unique,” said Peter Arnold, who graduated in 1982 from Bethesda’s Landon School, the all-boys prep school in suburban Maryland where Jacoby taught math for more than two decades. “You couldn’t wait to see how he’d use a little craziness to teach the finer points of algebra and geometry.”

Jacoby beguiled rowdy seventh- and eighth-grade boys with tales of his “dear Aunt Sally” — a mnemonic device the teacher used to remind his students to “divide, add and subtract” only after they multiplied the numbers in an equation. It’s been 45 years since Arnold sat in Jacoby’s chalk-covered classroom, but he still remembers the tricks his teacher taught him, including a shortcut for squaring two-digit numbers in a matter of seconds.

Jacoby was 93 when he died on April 11 after a brief battle with covid-19, said Jim Weiss, a longtime friend and former head of Landon’s lower school.

“It came very fast,” Weiss said of the illness. Jacoby, who was living in a retirement community in Gaithersburg, was rushed to the hospital on a Friday afternoon.

He died the next day, Weiss said.

Jacoby was born in Brooklyn and grew up in Westport, Conn. His life was defined by service — first in the U.S. Navy during World War II. He joined the Air Force after meeting a recruiter on campus as a student at Trinity College, and fought for roughly a year in Korea, said Lowell Davis, a friend and former Landon athletic director. As a member of the Air Force Reserve, Jacoby climbed the ranks to lieutenant colonel.

But in 1955, Jacoby turned his attention to educating children. He never married or had children of his own — instead, he dedicated the rest of his life to his students, friends said.

During his 65-year career — the longest in Landon’s history — Jacoby served many roles. In addition to math teacher, he was head of Landon’s middle school. As varsity tennis coach, he led the squad to 42 Interstate Athletic Conference titles and produced more than 20 individual championships and team titles, according to a letter Jim Neill, Landon’s headmaster, sent to the community after Jacoby’s death.

Even after he retired, Jacoby stayed close to campus, attending nearly every tennis match and keeping stats at football and basketball games.

“We wouldn’t let him go,” Davis said. “When I became the head football coach in 1972, Mac Jacoby came to every one of my football games for 30 years.”

His attendance waned as he got older, said Davis, who took turns with Weiss driving Jacoby to doctor’s appointments and events on campus. But, even into his 90s, Jacoby refused to miss a tennis season. On a cool day in early March, Jacoby made his way to the school’s court that bears his name, leaned against a fence and took notes, Davis said. It was one of the last interactions he had with the boys.

Jacoby wasn’t just a fixture at Landon, friends said. He was Landon.

“Isaac Newton famously talked of seeing further because he stood on the shoulders of giants. That’s how so many of us feel about Mac’s legacy,” Arnold said. “He helped make us better people and for that, we’ll always be grateful.”