Want to know how to discourage your opponent on a tennis court? Try 5-all in a tough, even, first set, then, falling behind, 15-40, while serving at serving three clean aces and an unreturnable serve to get out of it, and a couple of more aces and a blazing service winner in the ensuing tie breaker.

That's what fourth-seeded Betty Stove did against Renata Tomanova yesterday afternoon, and that crowd-pleasing stretch of "Bionic Women" serving turned their tight second-round match in the $100,000 Virginia Slims of Washington Tournament Stove's way, 7-6, 6-4.

Tomanova was as discourage as if she had been served with a subpoena.

As Stove blistered deliveries by her down the middle, wide to the backhand and wide to the forehand in turn, Tomanova looked first impassive, then pained, later exasperated, and finally bemused.

She gave a wonderful little smirk to the gallery after knocking a backhand retrun way long off a fine second serve on the final point of the nine-points tie breaker that she lost, 5-1. It was the only second serve she had seen in awhile, and it was better than most players' first deliveries.

"What can you do if you're walking past a barn and it collapses on your head?" Tomanova's expression seemed to say. "Just try to enjoy the esthetics of the way the wreckagefalls."

What did she think of Stove's serve, she was asked. "It's disgusting," she said, and then laughed agreeably, as it appreciating a joke even if it was on her. "It's a great advantage. It decided the match."

Only two singles matches were played during the matinee session of the 32-woman tournament at George Washington University's Smith Center. In the other, diminutive Linky Boshoff of South Africa also moved into the second round by defeating Australian Cynthia Doerner, 3-6, 6-2, 6-3.

The entertaining Stove-Tomanova match brought together two Leaning Towers of Crunch. Both players are big, powerful and improving.

The 22-year-old Tomanova, a native of Jindrichuv Hrabec, Czechoslovakia, is a statuesque 5-foot-6 and 130 pounds.

She is an accoumplished clay court player - winner of the German Open in 1975, and runner-up in the German and French last year - and learned a great deal about playing on fast courts by spending most of the last month in Australia, playing on grass. (She was runner-up in the Australian Open in January, 1976, but gained more this trip by playing toughter competition.)

Stove, a 31-year-old from Alblasserdam, Holland, is 6-0 and 155 pounds, but decidedly does not like the nickname given to her by a TV commentator "Big Bad Betty." ("I don't think I'm bad, do you? I kind of resent it.")

Contrary to the experience of most players who have become heavily involved in tennis administration, Stove's game has improved since she became president of the Women's Tennis Association (WTA) September. She climbed into the eunofficial world top 10 rankings for the first time on the strength of her 1976 record, and since Forest Hills has been runner-up to Virginia Wade at Atlanta, won Tokyo overe Margaret Court and was runner up to Martina Navratilova in Sydney.

She has also maintained her outstanding doubles record of the last few years.

Stove's game yesterday was inconsistent. For example, after taking the first set with that burst of superserving, she broke Tomanova in the first game of the second set and then immediately lost her serve, undone by two double-faults.

She made some terrific shots - hard, flat forehands and sliced backhands, superbly angled overheads, and a particularly memorable drop shot return of serve winner - but blew just as many easy ones.

She was never behind after breaking Tomanova again in the third game of the second set, a game that was a miniature match in itself. She cashed in on her sixth break point, after six deuces, Tomanova having had two game points. But even though she stayed ahead, Stove had to scramble all the way.

A bright and personable woman of many diverse interests, Stove is a thinking woman's tennis player, and she looked at her victory analytically.

"I served really well in that one important stretch, but I missed a lot of first serves on other points. I don't think I served that well overall," she admitted.

"It was my first match of a new season. You're always trying to figure out what to do in that situation," she said. "I've been practicing in Europe after playing outdoors in Australia. It takes some time to get used to the carpet, the different balls, a warm arena, a whole new set of circumstances.

"I'm glad about this match because I learned a lot. I played a lot of loose points, and now I think back on them. Like that drop shot return winner - a great shot, but a very bad percentage play in the situation. Do that against Chris Evert and you're dead.

"That's what's so fascinating about tennis. You're always learning. Every day is different, because you and your opponent both change. The ball is round, as they say. So you have to try to figure out how it's going to bounce."